SEC Info  
    Home      Search      My Interests      Help      Sign In      Please Sign In

8X8 Inc./DE – ‘10-Q’ for 6/30/22 – ‘EX-101.DEF’

On:  Friday, 7/29/22, at 9:04pm ET   ·   As of:  8/1/22   ·   For:  6/30/22   ·   Accession #:  1023731-22-169   ·   File #:  1-38312

Previous ‘10-Q’:  ‘10-Q’ on 2/3/22 for 12/31/21   ·   Next:  ‘10-Q’ on 11/3/22 for 9/30/22   ·   Latest:  ‘10-Q’ on 2/1/24 for 12/31/23   ·   2 References:   

Find Words in Filings emoji
 
  in    Show  and   Hints

  As Of               Filer                 Filing    For·On·As Docs:Size

 8/01/22  8X8 Inc./DE                       10-Q        6/30/22   71:6M

Quarterly Report   —   Form 10-Q

Filing Table of Contents

Document/Exhibit                   Description                      Pages   Size 

 1: 10-Q        Quarterly Report                                    HTML   1.15M 
 2: EX-31.1     Certification -- §302 - SOA'02                      HTML     24K 
 3: EX-31.2     Certification -- §302 - SOA'02                      HTML     23K 
 4: EX-32.1     Certification -- §906 - SOA'02                      HTML     21K 
 5: EX-32.2     Certification -- §906 - SOA'02                      HTML     21K 
11: R1          Cover Page                                          HTML     73K 
12: R2          Condensed Consolidated Balance Sheets               HTML    142K 
13: R3          Condensed Consolidated Statements of Operations     HTML     88K 
14: R4          Condensed Consolidated Statements of Comprehensive  HTML     42K 
                Loss                                                             
15: R5          Condensed Consolidated Statements of Stockholders'  HTML     64K 
                Equity                                                           
16: R6          Condensed Consolidated Statements of Cash Flows     HTML    124K 
17: R7          The Company and Significant Accounting Policies     HTML     32K 
18: R8          Revenue Recognition                                 HTML     37K 
19: R9          Fair Value Measurements                             HTML    108K 
20: R10         Intangible Assets and Goodwill                      HTML     48K 
21: R11         Leases                                              HTML     46K 
22: R12         Commitments and Contingencies                       HTML     32K 
23: R13         Convertible Senior Notes and Capped Calls           HTML     52K 
24: R14         Stock-Based Compensation and Stockholders' Equity   HTML     66K 
25: R15         Income Taxes                                        HTML     24K 
26: R16         Net Loss Per Share                                  HTML     34K 
27: R17         Geographical Information                            HTML     37K 
28: R18         Acquisitions                                        HTML     23K 
29: R19         The Company and Significant Accounting Policies     HTML     37K 
                (Policies)                                                       
30: R20         Revenue Recognition (Tables)                        HTML     29K 
31: R21         Fair Value Measurements (Tables)                    HTML    105K 
32: R22         Intangible Assets and Goodwill (Tables)             HTML     56K 
33: R23         Leases (Tables)                                     HTML     48K 
34: R24         Convertible Senior Notes and Capped Calls (Tables)  HTML     36K 
35: R25         Stock-Based Compensation and Stockholders' Equity   HTML     60K 
                (Tables)                                                         
36: R26         Net Loss Per Share (Tables)                         HTML     36K 
37: R27         Geographical Information (Tables)                   HTML     37K 
38: R28         THE COMPANY AND SIGNIFICANT ACCOUNTING POLICIES -   HTML     55K 
                Narrative (Details)                                              
39: R29         REVENUE RECOGNITION - Contract Balances (Details)   HTML     33K 
40: R30         REVENUE RECOGNITION - Narrative (Details)           HTML     26K 
41: R31         REVENUE RECOGNITION - Remaining Performance         HTML     36K 
                Obligation (Details)                                             
42: R32         FAIR VALUE MEASUREMENTS - Cash, Cash Equivalents    HTML    112K 
                and Investments with Hierarchy (Details)                         
43: R33         FAIR VALUE MEASUREMENTS - Narrative (Details)       HTML     27K 
44: R34         INTANGIBLE ASSETS AND GOODWILL- Schedule Of         HTML     36K 
                Intangibles (Details)                                            
45: R35         INTANGIBLE ASSETS AND GOODWILL - Narrative          HTML     28K 
                (Details)                                                        
46: R36         INTANGIBLE ASSETS AND GOODWILL - Schedule Of        HTML     33K 
                Future Amortization Of Intangibles (Details)                     
47: R37         INTANGIBLE ASSETS AND GOODWILL - Changes in         HTML     28K 
                Carrying Amount of Goodwill by Location (Details)                
48: R38         LEASES - Components of Lease Right-of-Use Assets    HTML     30K 
                and Liabilities (Details)                                        
49: R39         LEASES - Operating Lease Expense (Details)          HTML     24K 
50: R40         LEASES - Narrative (Details)                        HTML     25K 
51: R41         LEASES - Supplemental Information (Details)         HTML     24K 
52: R42         LEASES - Maturity of Lease Liabilities (Details)    HTML     39K 
53: R43         Commitments and Contingencies (Details)             HTML     24K 
54: R44         CONVERTIBLE SENIOR NOTES AND CAPPED CALLS -         HTML     88K 
                Narrative (Details)                                              
55: R45         CONVERTIBLE SENIOR NOTES AND CAPPED CALLS -         HTML     33K 
                Carrying Amount of the Liability Component                       
                (Details)                                                        
56: R46         CONVERTIBLE SENIOR NOTES AND CAPPED CALLS -         HTML     33K 
                Interest Expense (Details)                                       
57: R47         STOCK-BASED COMPENSATION AND STOCKHOLDERS' EQUITY   HTML     82K 
                - Narrative (Details)                                            
58: R48         STOCK-BASED COMPENSATION AND STOCKHOLDERS' EQUITY   HTML     34K 
                - Stock-Based Compensation Expense By Statement Of               
                Operations (Details)                                             
59: R49         STOCK-BASED COMPENSATION AND STOCKHOLDERS' EQUITY   HTML     51K 
                - Option Activity (Details)                                      
60: R50         STOCK-BASED COMPENSATION AND STOCKHOLDERS' EQUITY   HTML     60K 
                - STOCK-BASED COMPENSATION AND STOCKHOLDERS'                     
                EQUITY - Restricted Stock Unit and Performance                   
                Stock Unit Activity (Details)                                    
61: R51         Income Taxes (Details)                              HTML     22K 
62: R52         NET LOSS PER SHARE - Basic and Diluted Net Income   HTML     52K 
                (Loss) Per Share (Details)                                       
63: R53         NET LOSS PER SHARE - Schedule of Antidilutive       HTML     30K 
                Awards (Details)                                                 
64: R54         Geographical Information (Details)                  HTML     33K 
65: R55         ACQUISITIONS - Narrative (Details)                  HTML     41K 
66: R9999       Uncategorized Items - eght-20220630.htm             HTML     40K 
69: XML         IDEA XML File -- Filing Summary                      XML    124K 
67: XML         XBRL Instance -- eght-20220630_htm                   XML   1.46M 
68: EXCEL       IDEA Workbook of Financial Reports                  XLSX    113K 
 7: EX-101.CAL  XBRL Calculations -- eght-20220630_cal               XML    179K 
 8: EX-101.DEF  XBRL Definitions -- eght-20220630_def                XML    432K 
 9: EX-101.LAB  XBRL Labels -- eght-20220630_lab                     XML   1.25M 
10: EX-101.PRE  XBRL Presentations -- eght-20220630_pre              XML    744K 
 6: EX-101.SCH  XBRL Schema -- eght-20220630                         XSD    119K 
70: JSON        XBRL Instance as JSON Data -- MetaLinks              361±   533K 
71: ZIP         XBRL Zipped Folder -- 0001023731-22-000169-xbrl      Zip    320K 


‘EX-101.DEF’   —   XBRL Definitions — eght-20220630_def


This Exhibit is an XBRL XML File.


                                                                                                                                                                                
<?xml version="1.0" encoding="windows-1252"?>
<!-- XBRL Document Created with Wdesk from Workiva -->
<!-- Copyright 2022 Workiva -->
<!-- r:98ee0c36-df1a-4810-a025-469fde421aeb,g:0b84da8e-991c-484e-a2a6-716f32d87172 -->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
<link:roleRef roleURI="http://8x8.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="eght-20220630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
<link:definitionLink xlink:role="http://8x8.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended" id="icd33ded0ce99454788399ea17e4fb185_CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_7dd11e7a-2438-4661-ba4f-714790f02ffb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_97d0ec92-d73d-4998-91c8-f93f074bb9c6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7dd11e7a-2438-4661-ba4f-714790f02ffb" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_97d0ec92-d73d-4998-91c8-f93f074bb9c6" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_e5c03be8-8cb6-4f9b-84bb-ff84ae131813" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingExpensesAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7dd11e7a-2438-4661-ba4f-714790f02ffb" xlink:to="loc_us-gaap_OperatingExpensesAbstract_e5c03be8-8cb6-4f9b-84bb-ff84ae131813" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_9f3790c4-e835-4230-8867-709feb5721b3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_e5c03be8-8cb6-4f9b-84bb-ff84ae131813" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_9f3790c4-e835-4230-8867-709feb5721b3" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_d5995226-1df2-434b-adb2-b3ccbaa8929a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_e5c03be8-8cb6-4f9b-84bb-ff84ae131813" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_d5995226-1df2-434b-adb2-b3ccbaa8929a" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_e5ded41b-23ac-4c05-9375-75d21a75c411" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SellingAndMarketingExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_e5c03be8-8cb6-4f9b-84bb-ff84ae131813" xlink:to="loc_us-gaap_SellingAndMarketingExpense_e5ded41b-23ac-4c05-9375-75d21a75c411" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_fd9c11bf-d48a-40b6-bf13-c060ec1f2339" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_e5c03be8-8cb6-4f9b-84bb-ff84ae131813" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_fd9c11bf-d48a-40b6-bf13-c060ec1f2339" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_08e75d6f-962d-41f8-ae21-ddea9a125904" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingExpenses"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_e5c03be8-8cb6-4f9b-84bb-ff84ae131813" xlink:to="loc_us-gaap_OperatingExpenses_08e75d6f-962d-41f8-ae21-ddea9a125904" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_10aedfcc-f8d1-462f-b43e-9399686c88f4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingIncomeLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7dd11e7a-2438-4661-ba4f-714790f02ffb" xlink:to="loc_us-gaap_OperatingIncomeLoss_10aedfcc-f8d1-462f-b43e-9399686c88f4" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_7eeb8e85-ef83-463f-8895-d6a6f9361eb5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NonoperatingIncomeExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7dd11e7a-2438-4661-ba4f-714790f02ffb" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_7eeb8e85-ef83-463f-8895-d6a6f9361eb5" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_6f29dc68-5458-4a69-ae9c-b8897078db75" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7dd11e7a-2438-4661-ba4f-714790f02ffb" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_6f29dc68-5458-4a69-ae9c-b8897078db75" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_b8c950ba-b99d-4bef-b54e-c693e0a730ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7dd11e7a-2438-4661-ba4f-714790f02ffb" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_b8c950ba-b99d-4bef-b54e-c693e0a730ac" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_04c28b20-c584-467e-84ee-b10d03acd56f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7dd11e7a-2438-4661-ba4f-714790f02ffb" xlink:to="loc_us-gaap_NetIncomeLoss_04c28b20-c584-467e-84ee-b10d03acd56f" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_859297ab-41b9-41ac-bf03-aa2167c14868" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7dd11e7a-2438-4661-ba4f-714790f02ffb" xlink:to="loc_us-gaap_EarningsPerShareAbstract_859297ab-41b9-41ac-bf03-aa2167c14868" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_5fc2ea0f-1a4f-48be-acea-e96e5561553d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareBasic"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_859297ab-41b9-41ac-bf03-aa2167c14868" xlink:to="loc_us-gaap_EarningsPerShareBasic_5fc2ea0f-1a4f-48be-acea-e96e5561553d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_0e775973-4785-400a-ad0e-9b2574c2eda1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EarningsPerShareDiluted"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_859297ab-41b9-41ac-bf03-aa2167c14868" xlink:to="loc_us-gaap_EarningsPerShareDiluted_0e775973-4785-400a-ad0e-9b2574c2eda1" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_5b249d50-89fe-4308-b0cb-486a2846b72a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7dd11e7a-2438-4661-ba4f-714790f02ffb" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_5b249d50-89fe-4308-b0cb-486a2846b72a" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_c83ccf15-8ca1-48d8-82ea-44eb52e1751c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_5b249d50-89fe-4308-b0cb-486a2846b72a" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_c83ccf15-8ca1-48d8-82ea-44eb52e1751c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_efcfe957-8ab7-413d-b641-0e456785a4f5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_5b249d50-89fe-4308-b0cb-486a2846b72a" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_efcfe957-8ab7-413d-b641-0e456785a4f5" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_66a389d1-20c7-47bd-979b-08731bf21d89" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_7dd11e7a-2438-4661-ba4f-714790f02ffb" xlink:to="loc_us-gaap_StatementTable_66a389d1-20c7-47bd-979b-08731bf21d89" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_9c2a5fbb-3f56-4b07-9c77-f21e360aa5fa" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_66a389d1-20c7-47bd-979b-08731bf21d89" xlink:to="loc_srt_ProductOrServiceAxis_9c2a5fbb-3f56-4b07-9c77-f21e360aa5fa" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_9c2a5fbb-3f56-4b07-9c77-f21e360aa5fa_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_9c2a5fbb-3f56-4b07-9c77-f21e360aa5fa" xlink:to="loc_srt_ProductsAndServicesDomain_9c2a5fbb-3f56-4b07-9c77-f21e360aa5fa_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_12ad4d20-fdfa-4fbe-a666-cf6dfade3ba1" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_9c2a5fbb-3f56-4b07-9c77-f21e360aa5fa" xlink:to="loc_srt_ProductsAndServicesDomain_12ad4d20-fdfa-4fbe-a666-cf6dfade3ba1" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_ebff9bed-b147-4156-a662-38f72fcb709a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ServiceMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_12ad4d20-fdfa-4fbe-a666-cf6dfade3ba1" xlink:to="loc_us-gaap_ServiceMember_ebff9bed-b147-4156-a662-38f72fcb709a" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_99a46e3a-cefe-4122-adbb-786dee370ece" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProductAndServiceOtherMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_12ad4d20-fdfa-4fbe-a666-cf6dfade3ba1" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_99a46e3a-cefe-4122-adbb-786dee370ece" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="simple" xlink:href="eght-20220630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY"/>
<link:definitionLink xlink:role="http://8x8.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="extended" id="i4539e8888a2f4b21afd41f8290ea06c4_CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_004061b2-678f-4824-979e-2cd569fdb85a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93dc870d-5110-4770-969e-192785ea0579" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_004061b2-678f-4824-979e-2cd569fdb85a" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93dc870d-5110-4770-969e-192785ea0579" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_4fe3d97c-cc3b-498d-9c80-af1819a584d9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93dc870d-5110-4770-969e-192785ea0579" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_4fe3d97c-cc3b-498d-9c80-af1819a584d9" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_0638cc18-73c4-4d88-a14c-9c6894a655cd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93dc870d-5110-4770-969e-192785ea0579" xlink:to="loc_us-gaap_StockholdersEquity_0638cc18-73c4-4d88-a14c-9c6894a655cd" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_86adae13-04f8-498b-9342-9f25d6d89c96" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93dc870d-5110-4770-969e-192785ea0579" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_86adae13-04f8-498b-9342-9f25d6d89c96" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_aac50323-fdb9-49c0-820b-4093a50e1da3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93dc870d-5110-4770-969e-192785ea0579" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_aac50323-fdb9-49c0-820b-4093a50e1da3" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_e3a164d9-5d63-45bb-af6c-e49cef080473" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93dc870d-5110-4770-969e-192785ea0579" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_e3a164d9-5d63-45bb-af6c-e49cef080473" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent_50d57bd4-2338-4c69-b095-6690bbb8bc71" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93dc870d-5110-4770-969e-192785ea0579" xlink:to="loc_us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent_50d57bd4-2338-4c69-b095-6690bbb8bc71" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_2ebf74cd-5efe-4433-aefc-5f77a70f011d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93dc870d-5110-4770-969e-192785ea0579" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_2ebf74cd-5efe-4433-aefc-5f77a70f011d" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_242b6bb2-6f8b-450c-bd36-3a7c78d697d8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93dc870d-5110-4770-969e-192785ea0579" xlink:to="loc_us-gaap_NetIncomeLoss_242b6bb2-6f8b-450c-bd36-3a7c78d697d8" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_0a8ade97-e46d-4682-9181-a8a60db28a71" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_13bbd007-52a8-4ca9-8110-56879e4600c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountingStandardsUpdateExtensibleList_e0bfb10e-4534-45a3-b919-433313321405" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountingStandardsUpdateExtensibleList"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93dc870d-5110-4770-969e-192785ea0579" xlink:to="loc_us-gaap_AccountingStandardsUpdateExtensibleList_e0bfb10e-4534-45a3-b919-433313321405" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_5c992b68-c4ef-40a5-9cda-dc5883b31341" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_004061b2-678f-4824-979e-2cd569fdb85a" xlink:to="loc_us-gaap_StatementTable_5c992b68-c4ef-40a5-9cda-dc5883b31341" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_6c145f20-588e-4f44-8506-2d86be4f9941" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_5c992b68-c4ef-40a5-9cda-dc5883b31341" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_6c145f20-588e-4f44-8506-2d86be4f9941" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_6c145f20-588e-4f44-8506-2d86be4f9941_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6c145f20-588e-4f44-8506-2d86be4f9941" xlink:to="loc_us-gaap_EquityComponentDomain_6c145f20-588e-4f44-8506-2d86be4f9941_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_c28aacd4-9e13-42c1-9178-c62b1f323dc9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6c145f20-588e-4f44-8506-2d86be4f9941" xlink:to="loc_us-gaap_EquityComponentDomain_c28aacd4-9e13-42c1-9178-c62b1f323dc9" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_992a02fc-8c25-4804-9299-e3604020329b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c28aacd4-9e13-42c1-9178-c62b1f323dc9" xlink:to="loc_us-gaap_CommonStockMember_992a02fc-8c25-4804-9299-e3604020329b" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_14ef7fae-cced-41f6-95e7-e1ad3c3e1021" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c28aacd4-9e13-42c1-9178-c62b1f323dc9" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_14ef7fae-cced-41f6-95e7-e1ad3c3e1021" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_900de3ef-a196-4b9c-b188-07110875df02" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c28aacd4-9e13-42c1-9178-c62b1f323dc9" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_900de3ef-a196-4b9c-b188-07110875df02" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_80fefa72-b450-458f-afa4-caa96b965e9b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c28aacd4-9e13-42c1-9178-c62b1f323dc9" xlink:to="loc_us-gaap_RetainedEarningsMember_80fefa72-b450-458f-afa4-caa96b965e9b" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_d993077c-be8f-4c1a-83c0-1e908e208ad3" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_5c992b68-c4ef-40a5-9cda-dc5883b31341" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_d993077c-be8f-4c1a-83c0-1e908e208ad3" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_d993077c-be8f-4c1a-83c0-1e908e208ad3_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_d993077c-be8f-4c1a-83c0-1e908e208ad3" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_d993077c-be8f-4c1a-83c0-1e908e208ad3_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_9791bba7-6182-4aac-a26e-3e9633bcad15" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_d993077c-be8f-4c1a-83c0-1e908e208ad3" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_9791bba7-6182-4aac-a26e-3e9633bcad15" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_c4a4d5ba-20d2-480f-a960-983fb2e9b337" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_9791bba7-6182-4aac-a26e-3e9633bcad15" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_c4a4d5ba-20d2-480f-a960-983fb2e9b337" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/THECOMPANYANDSIGNIFICANTACCOUNTINGPOLICIESNarrativeDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#THECOMPANYANDSIGNIFICANTACCOUNTINGPOLICIESNarrativeDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/THECOMPANYANDSIGNIFICANTACCOUNTINGPOLICIESNarrativeDetails" xlink:type="extended" id="i8f250bd87c554dc6945c0b09291bfb91_THECOMPANYANDSIGNIFICANTACCOUNTINGPOLICIESNarrativeDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_9bf55199-9903-4bf4-8755-f95718b42dd0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_ed9e0c23-d153-48ae-9ba0-52c1086c12f0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NumberOfReportableSegments"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_9bf55199-9903-4bf4-8755-f95718b42dd0" xlink:to="loc_us-gaap_NumberOfReportableSegments_ed9e0c23-d153-48ae-9ba0-52c1086c12f0" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_OutOfPeriodAdjustmentsAmount_58f3aafb-8e33-474b-bd7a-438679f58a9e" xlink:href="eght-20220630.xsd#eght_OutOfPeriodAdjustmentsAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_9bf55199-9903-4bf4-8755-f95718b42dd0" xlink:to="loc_eght_OutOfPeriodAdjustmentsAmount_58f3aafb-8e33-474b-bd7a-438679f58a9e" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_3a820e86-a158-445f-9f27-bb2233406d4f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_9bf55199-9903-4bf4-8755-f95718b42dd0" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_3a820e86-a158-445f-9f27-bb2233406d4f" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_c5fa69a2-a904-4073-ad04-d0f6d3961557" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_9bf55199-9903-4bf4-8755-f95718b42dd0" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_c5fa69a2-a904-4073-ad04-d0f6d3961557" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNet_19977a88-c603-4f0b-bcea-02fe509826d1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerAssetNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_9bf55199-9903-4bf4-8755-f95718b42dd0" xlink:to="loc_us-gaap_ContractWithCustomerAssetNet_19977a88-c603-4f0b-bcea-02fe509826d1" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_33d82f9d-c326-431d-a629-b2a4097197fb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_9bf55199-9903-4bf4-8755-f95718b42dd0" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_33d82f9d-c326-431d-a629-b2a4097197fb" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_bae5c6df-04cd-45bb-905f-c0d996cbdc39" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_9bf55199-9903-4bf4-8755-f95718b42dd0" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_bae5c6df-04cd-45bb-905f-c0d996cbdc39" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_8fc7b975-f9d7-417e-923d-a777bd166617" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapital"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_9bf55199-9903-4bf4-8755-f95718b42dd0" xlink:to="loc_us-gaap_AdditionalPaidInCapital_8fc7b975-f9d7-417e-923d-a777bd166617" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_54676f5f-c8dc-49d8-abb4-1f8203bbf653" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SeniorNotes"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_9bf55199-9903-4bf4-8755-f95718b42dd0" xlink:to="loc_us-gaap_SeniorNotes_54676f5f-c8dc-49d8-abb4-1f8203bbf653" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_2a22751a-6ce6-4e71-a91d-a34e8bb891d0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_9bf55199-9903-4bf4-8755-f95718b42dd0" xlink:to="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_2a22751a-6ce6-4e71-a91d-a34e8bb891d0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RestatementAxis_88bf183e-1548-4567-8745-e815b1b1fde2" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RestatementAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_2a22751a-6ce6-4e71-a91d-a34e8bb891d0" xlink:to="loc_srt_RestatementAxis_88bf183e-1548-4567-8745-e815b1b1fde2" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_88bf183e-1548-4567-8745-e815b1b1fde2_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RestatementDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RestatementAxis_88bf183e-1548-4567-8745-e815b1b1fde2" xlink:to="loc_srt_RestatementDomain_88bf183e-1548-4567-8745-e815b1b1fde2_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RestatementDomain_752d411a-6e73-4bff-a059-840fbbba760d" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RestatementDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RestatementAxis_88bf183e-1548-4567-8745-e815b1b1fde2" xlink:to="loc_srt_RestatementDomain_752d411a-6e73-4bff-a059-840fbbba760d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_94507dc8-8305-4181-bca0-90e79dcb4d22" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_752d411a-6e73-4bff-a059-840fbbba760d" xlink:to="loc_srt_RevisionOfPriorPeriodErrorCorrectionAdjustmentMember_94507dc8-8305-4181-bca0-90e79dcb4d22" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RevisionOfPriorPeriodAccountingStandardsUpdateAdjustmentMember_49f79ad5-7b9c-497d-9e22-1301e8e7e408" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RevisionOfPriorPeriodAccountingStandardsUpdateAdjustmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RestatementDomain_752d411a-6e73-4bff-a059-840fbbba760d" xlink:to="loc_srt_RevisionOfPriorPeriodAccountingStandardsUpdateAdjustmentMember_49f79ad5-7b9c-497d-9e22-1301e8e7e408" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_95218235-5df1-45cb-82b7-4e4f95c687e5" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_2a22751a-6ce6-4e71-a91d-a34e8bb891d0" xlink:to="loc_srt_ProductOrServiceAxis_95218235-5df1-45cb-82b7-4e4f95c687e5" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_95218235-5df1-45cb-82b7-4e4f95c687e5_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_95218235-5df1-45cb-82b7-4e4f95c687e5" xlink:to="loc_srt_ProductsAndServicesDomain_95218235-5df1-45cb-82b7-4e4f95c687e5_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_03b5edbc-06cd-41c2-8bbf-982dedad70ed" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_95218235-5df1-45cb-82b7-4e4f95c687e5" xlink:to="loc_srt_ProductsAndServicesDomain_03b5edbc-06cd-41c2-8bbf-982dedad70ed" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_712a6914-a9a9-4a0b-a79b-cb4f7c5a2887" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ServiceMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_03b5edbc-06cd-41c2-8bbf-982dedad70ed" xlink:to="loc_us-gaap_ServiceMember_712a6914-a9a9-4a0b-a79b-cb4f7c5a2887" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/REVENUERECOGNITIONRemainingPerformanceObligationDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#REVENUERECOGNITIONRemainingPerformanceObligationDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/REVENUERECOGNITIONRemainingPerformanceObligationDetails" xlink:type="extended" id="i5fc5ee42182144f4a743eeda5fd5d281_REVENUERECOGNITIONRemainingPerformanceObligationDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_RevenueSubscriptionTerm_15bcae07-6f3d-4ae3-871e-8361135f6e94" xlink:href="eght-20220630.xsd#eght_RevenueSubscriptionTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:to="loc_eght_RevenueSubscriptionTerm_15bcae07-6f3d-4ae3-871e-8361135f6e94" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_cd18c7d5-85a8-4a3b-a602-395d36f5711e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_cd18c7d5-85a8-4a3b-a602-395d36f5711e" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_57af047f-b394-402c-b0b7-7992cb1fcdb6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_57af047f-b394-402c-b0b7-7992cb1fcdb6" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_5377f2fa-b477-41bf-bfcc-9e3488ed530a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_5377f2fa-b477-41bf-bfcc-9e3488ed530a" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1f388a5c-e2cf-4a69-9e3e-5e3193aea631" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1f388a5c-e2cf-4a69-9e3e-5e3193aea631" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_1c83a852-f0ef-4116-a4ca-b5c03bfc6411" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1f388a5c-e2cf-4a69-9e3e-5e3193aea631" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_1c83a852-f0ef-4116-a4ca-b5c03bfc6411" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_d4f6fb7e-24d0-459c-9818-6080e07f9391" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1f388a5c-e2cf-4a69-9e3e-5e3193aea631" xlink:to="loc_srt_RangeAxis_d4f6fb7e-24d0-459c-9818-6080e07f9391" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d4f6fb7e-24d0-459c-9818-6080e07f9391_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_d4f6fb7e-24d0-459c-9818-6080e07f9391" xlink:to="loc_srt_RangeMember_d4f6fb7e-24d0-459c-9818-6080e07f9391_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_3d2cb539-90ae-42cf-bf5b-630bed395c70" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_d4f6fb7e-24d0-459c-9818-6080e07f9391" xlink:to="loc_srt_RangeMember_3d2cb539-90ae-42cf-bf5b-630bed395c70" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_5b4caeb8-35ab-4697-b5f4-e3c38aa8201f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_3d2cb539-90ae-42cf-bf5b-630bed395c70" xlink:to="loc_srt_MinimumMember_5b4caeb8-35ab-4697-b5f4-e3c38aa8201f" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_89103639-aadf-4cb7-a7dc-c13dfe4ed391" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_3d2cb539-90ae-42cf-bf5b-630bed395c70" xlink:to="loc_srt_MaximumMember_89103639-aadf-4cb7-a7dc-c13dfe4ed391" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/REVENUERECOGNITIONRemainingPerformanceObligationDetails_1" xlink:type="simple" xlink:href="eght-20220630.xsd#REVENUERECOGNITIONRemainingPerformanceObligationDetails_1"/>
<link:definitionLink xlink:role="http://8x8.com/role/REVENUERECOGNITIONRemainingPerformanceObligationDetails_1" xlink:type="extended" id="ibef8b246c8c047b395957f3b32daab85_REVENUERECOGNITIONRemainingPerformanceObligationDetails_1">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_RevenueSubscriptionTerm_15bcae07-6f3d-4ae3-871e-8361135f6e94" xlink:href="eght-20220630.xsd#eght_RevenueSubscriptionTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:to="loc_eght_RevenueSubscriptionTerm_15bcae07-6f3d-4ae3-871e-8361135f6e94" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_cd18c7d5-85a8-4a3b-a602-395d36f5711e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_cd18c7d5-85a8-4a3b-a602-395d36f5711e" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_57af047f-b394-402c-b0b7-7992cb1fcdb6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_57af047f-b394-402c-b0b7-7992cb1fcdb6" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_5377f2fa-b477-41bf-bfcc-9e3488ed530a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_5377f2fa-b477-41bf-bfcc-9e3488ed530a" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1f388a5c-e2cf-4a69-9e3e-5e3193aea631" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_6c888845-c571-4872-89ac-38f48e4a02d3" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1f388a5c-e2cf-4a69-9e3e-5e3193aea631" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_d4f6fb7e-24d0-459c-9818-6080e07f9391" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1f388a5c-e2cf-4a69-9e3e-5e3193aea631" xlink:to="loc_srt_RangeAxis_d4f6fb7e-24d0-459c-9818-6080e07f9391" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d4f6fb7e-24d0-459c-9818-6080e07f9391_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_d4f6fb7e-24d0-459c-9818-6080e07f9391" xlink:to="loc_srt_RangeMember_d4f6fb7e-24d0-459c-9818-6080e07f9391_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_3d2cb539-90ae-42cf-bf5b-630bed395c70" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_d4f6fb7e-24d0-459c-9818-6080e07f9391" xlink:to="loc_srt_RangeMember_3d2cb539-90ae-42cf-bf5b-630bed395c70" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_5b4caeb8-35ab-4697-b5f4-e3c38aa8201f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_3d2cb539-90ae-42cf-bf5b-630bed395c70" xlink:to="loc_srt_MinimumMember_5b4caeb8-35ab-4697-b5f4-e3c38aa8201f" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_89103639-aadf-4cb7-a7dc-c13dfe4ed391" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_3d2cb539-90ae-42cf-bf5b-630bed395c70" xlink:to="loc_srt_MaximumMember_89103639-aadf-4cb7-a7dc-c13dfe4ed391" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/FAIRVALUEMEASUREMENTSCashCashEquivalentsandInvestmentswithHierarchyDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#FAIRVALUEMEASUREMENTSCashCashEquivalentsandInvestmentswithHierarchyDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/FAIRVALUEMEASUREMENTSCashCashEquivalentsandInvestmentswithHierarchyDetails" xlink:type="extended" id="i0c6716ba8b1b49bc94042fdf0c9c8e8e_FAIRVALUEMEASUREMENTSCashCashEquivalentsandInvestmentswithHierarchyDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4550eeb7-567a-4740-b539-db6b5abfb6ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_d25ebdcd-f2df-43ad-9b51-284343d6e967" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4550eeb7-567a-4740-b539-db6b5abfb6ec" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_d25ebdcd-f2df-43ad-9b51-284343d6e967" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_776cc7fa-1da4-417b-8367-b66ac2dbe461" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4550eeb7-567a-4740-b539-db6b5abfb6ec" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_776cc7fa-1da4-417b-8367-b66ac2dbe461" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_128485bf-984b-4550-8316-b30b7acb9182" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4550eeb7-567a-4740-b539-db6b5abfb6ec" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_128485bf-984b-4550-8316-b30b7acb9182" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_d6817a51-b9a5-4366-a941-f035c1a1c767" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4550eeb7-567a-4740-b539-db6b5abfb6ec" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_d6817a51-b9a5-4366-a941-f035c1a1c767" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_5aff4375-8e88-44b4-a3ae-07552a5842d8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4550eeb7-567a-4740-b539-db6b5abfb6ec" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_5aff4375-8e88-44b4-a3ae-07552a5842d8" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_1361a728-2a6e-4d6c-ab6c-0569f0e6d843" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4550eeb7-567a-4740-b539-db6b5abfb6ec" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_1361a728-2a6e-4d6c-ab6c-0569f0e6d843" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_CashCashEquivalentsandDebtSecuritiesAvailableforsaleAmortizedCost_3d5a62d5-68b7-45cd-aa24-9b341a27b148" xlink:href="eght-20220630.xsd#eght_CashCashEquivalentsandDebtSecuritiesAvailableforsaleAmortizedCost"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4550eeb7-567a-4740-b539-db6b5abfb6ec" xlink:to="loc_eght_CashCashEquivalentsandDebtSecuritiesAvailableforsaleAmortizedCost_3d5a62d5-68b7-45cd-aa24-9b341a27b148" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_CashCashEquivalentsandDebtSecuritiesAvailableforsale_9642eb6f-32de-4028-96f4-6a197605c2de" xlink:href="eght-20220630.xsd#eght_CashCashEquivalentsandDebtSecuritiesAvailableforsale"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4550eeb7-567a-4740-b539-db6b5abfb6ec" xlink:to="loc_eght_CashCashEquivalentsandDebtSecuritiesAvailableforsale_9642eb6f-32de-4028-96f4-6a197605c2de" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_bb6ba61a-39ac-48cc-b122-1db63e9a6fc0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4550eeb7-567a-4740-b539-db6b5abfb6ec" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_bb6ba61a-39ac-48cc-b122-1db63e9a6fc0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_015edf45-03cc-4f08-8609-971acacf7011" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BalanceSheetLocationAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_bb6ba61a-39ac-48cc-b122-1db63e9a6fc0" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_015edf45-03cc-4f08-8609-971acacf7011" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_015edf45-03cc-4f08-8609-971acacf7011_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BalanceSheetLocationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_015edf45-03cc-4f08-8609-971acacf7011" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_015edf45-03cc-4f08-8609-971acacf7011_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_5f4d745e-2019-4c75-9804-c4e81ca6a154" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BalanceSheetLocationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_015edf45-03cc-4f08-8609-971acacf7011" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_5f4d745e-2019-4c75-9804-c4e81ca6a154" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_cb7b7a9c-2ce9-41d4-95f6-0c21719e2b32" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_5f4d745e-2019-4c75-9804-c4e81ca6a154" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_cb7b7a9c-2ce9-41d4-95f6-0c21719e2b32" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_RestrictedCashMember_3977ecfc-bb32-4446-a337-208e2b22dc89" xlink:href="eght-20220630.xsd#eght_RestrictedCashMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_5f4d745e-2019-4c75-9804-c4e81ca6a154" xlink:to="loc_eght_RestrictedCashMember_3977ecfc-bb32-4446-a337-208e2b22dc89" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_1f190f97-b62e-4ef6-91c0-3ba0bfc081c4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermInvestmentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_5f4d745e-2019-4c75-9804-c4e81ca6a154" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_1f190f97-b62e-4ef6-91c0-3ba0bfc081c4" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_LongtermInvestmentsMember_623138d7-4f48-4b2f-8c8e-3024a56c289d" xlink:href="eght-20220630.xsd#eght_LongtermInvestmentsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_5f4d745e-2019-4c75-9804-c4e81ca6a154" xlink:to="loc_eght_LongtermInvestmentsMember_623138d7-4f48-4b2f-8c8e-3024a56c289d" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_01302fdf-650f-45de-81b9-fa7ab1be1daf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_bb6ba61a-39ac-48cc-b122-1db63e9a6fc0" xlink:to="loc_us-gaap_FinancialInstrumentAxis_01302fdf-650f-45de-81b9-fa7ab1be1daf" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01302fdf-650f-45de-81b9-fa7ab1be1daf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01302fdf-650f-45de-81b9-fa7ab1be1daf" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_01302fdf-650f-45de-81b9-fa7ab1be1daf_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4213b253-6426-48f3-a563-d772708dd97d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_01302fdf-650f-45de-81b9-fa7ab1be1daf" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4213b253-6426-48f3-a563-d772708dd97d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashMember_bc38e553-015b-4d38-833a-6e9e51c59b4e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4213b253-6426-48f3-a563-d772708dd97d" xlink:to="loc_us-gaap_CashMember_bc38e553-015b-4d38-833a-6e9e51c59b4e" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_bf1dad43-4deb-4223-82f3-4ee45f36c1c0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MoneyMarketFundsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4213b253-6426-48f3-a563-d772708dd97d" xlink:to="loc_us-gaap_MoneyMarketFundsMember_bf1dad43-4deb-4223-82f3-4ee45f36c1c0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_6af128e0-a15f-43d1-97a5-9890e24a6961" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USTreasurySecuritiesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4213b253-6426-48f3-a563-d772708dd97d" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_6af128e0-a15f-43d1-97a5-9890e24a6961" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_a0570529-b7d4-4a68-a747-b5269bad5609" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CertificatesOfDepositMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4213b253-6426-48f3-a563-d772708dd97d" xlink:to="loc_us-gaap_CertificatesOfDepositMember_a0570529-b7d4-4a68-a747-b5269bad5609" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_7a287314-1792-4e20-8b74-d830c5a9f7c9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommercialPaperMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4213b253-6426-48f3-a563-d772708dd97d" xlink:to="loc_us-gaap_CommercialPaperMember_7a287314-1792-4e20-8b74-d830c5a9f7c9" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_b69db9ca-3b8d-487e-b0af-c3d2d79e2b13" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_4213b253-6426-48f3-a563-d772708dd97d" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_b69db9ca-3b8d-487e-b0af-c3d2d79e2b13" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_880cf935-0c3b-46b2-b02a-4ee311c57b01" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_bb6ba61a-39ac-48cc-b122-1db63e9a6fc0" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_880cf935-0c3b-46b2-b02a-4ee311c57b01" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_880cf935-0c3b-46b2-b02a-4ee311c57b01_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_880cf935-0c3b-46b2-b02a-4ee311c57b01" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_880cf935-0c3b-46b2-b02a-4ee311c57b01_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_012da2d0-e1ef-431b-91f4-ced8c1a03db0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_880cf935-0c3b-46b2-b02a-4ee311c57b01" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_012da2d0-e1ef-431b-91f4-ced8c1a03db0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_e7f6153d-9daa-4aac-8692-32237d1f4c19" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel1Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_012da2d0-e1ef-431b-91f4-ced8c1a03db0" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_e7f6153d-9daa-4aac-8692-32237d1f4c19" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_3c046eb7-71c9-4c73-8212-532b69bbcdc9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel2Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_012da2d0-e1ef-431b-91f4-ced8c1a03db0" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_3c046eb7-71c9-4c73-8212-532b69bbcdc9" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/FAIRVALUEMEASUREMENTSNarrativeDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#FAIRVALUEMEASUREMENTSNarrativeDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/FAIRVALUEMEASUREMENTSNarrativeDetails" xlink:type="extended" id="iba5a8c75608642f3ad749fea480e9f3b_FAIRVALUEMEASUREMENTSNarrativeDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_55e0dce4-a959-4a18-9455-33252a0a424f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_0028495e-4f8c-402d-af27-cf4584de1e73" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_55e0dce4-a959-4a18-9455-33252a0a424f" xlink:to="loc_us-gaap_DebtInstrumentFairValue_0028495e-4f8c-402d-af27-cf4584de1e73" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_8c796bf1-0138-4556-afc4-de44af3a3132" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_55e0dce4-a959-4a18-9455-33252a0a424f" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_8c796bf1-0138-4556-afc4-de44af3a3132" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2af67bc9-fefc-440d-b189-17e94463906c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_8c796bf1-0138-4556-afc4-de44af3a3132" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2af67bc9-fefc-440d-b189-17e94463906c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_2af67bc9-fefc-440d-b189-17e94463906c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2af67bc9-fefc-440d-b189-17e94463906c" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_2af67bc9-fefc-440d-b189-17e94463906c_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_e7884500-e550-4f11-af48-c0652368a231" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2af67bc9-fefc-440d-b189-17e94463906c" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_e7884500-e550-4f11-af48-c0652368a231" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_695e57ea-2600-4f40-a8f8-f36d2f3b1b93" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel2Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_e7884500-e550-4f11-af48-c0652368a231" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_695e57ea-2600-4f40-a8f8-f36d2f3b1b93" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_4d6a466b-bd1a-443d-9ab2-1d09573a5946" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_8c796bf1-0138-4556-afc4-de44af3a3132" xlink:to="loc_us-gaap_DebtInstrumentAxis_4d6a466b-bd1a-443d-9ab2-1d09573a5946" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_4d6a466b-bd1a-443d-9ab2-1d09573a5946_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_4d6a466b-bd1a-443d-9ab2-1d09573a5946" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_4d6a466b-bd1a-443d-9ab2-1d09573a5946_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_5b063465-2a5b-4a4c-ac98-02845117f909" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_4d6a466b-bd1a-443d-9ab2-1d09573a5946" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_5b063465-2a5b-4a4c-ac98-02845117f909" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_InitialNotesMember_f0748a11-0c61-48d5-a428-01dafffc5e9c" xlink:href="eght-20220630.xsd#eght_InitialNotesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_5b063465-2a5b-4a4c-ac98-02845117f909" xlink:to="loc_eght_InitialNotesMember_f0748a11-0c61-48d5-a428-01dafffc5e9c" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_c5072ac8-91fc-4830-b911-a2aad64e3408" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_8c796bf1-0138-4556-afc4-de44af3a3132" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_c5072ac8-91fc-4830-b911-a2aad64e3408" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_c5072ac8-91fc-4830-b911-a2aad64e3408_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_c5072ac8-91fc-4830-b911-a2aad64e3408" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_c5072ac8-91fc-4830-b911-a2aad64e3408_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_10699b06-0ef6-4372-b111-f22cbea0ea5b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_c5072ac8-91fc-4830-b911-a2aad64e3408" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_10699b06-0ef6-4372-b111-f22cbea0ea5b" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_ecb517af-e335-4cef-9d3d-b5001a053e8b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_10699b06-0ef6-4372-b111-f22cbea0ea5b" xlink:to="loc_us-gaap_ConvertibleDebtMember_ecb517af-e335-4cef-9d3d-b5001a053e8b" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/INTANGIBLEASSETSANDGOODWILLScheduleOfIntangiblesDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#INTANGIBLEASSETSANDGOODWILLScheduleOfIntangiblesDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/INTANGIBLEASSETSANDGOODWILLScheduleOfIntangiblesDetails" xlink:type="extended" id="ie43339aa470d42e299ef9a7954ef3bce_INTANGIBLEASSETSANDGOODWILLScheduleOfIntangiblesDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_dd21600f-3420-48c7-a94d-bf44b8f1f89d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_fcfdab5e-e1d1-48cc-bdbd-6fc340dc3800" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_dd21600f-3420-48c7-a94d-bf44b8f1f89d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_fcfdab5e-e1d1-48cc-bdbd-6fc340dc3800" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_0eaaa737-f8f2-4d99-b286-a2adce7c1dce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_dd21600f-3420-48c7-a94d-bf44b8f1f89d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_0eaaa737-f8f2-4d99-b286-a2adce7c1dce" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_47dab75b-2399-421b-b314-8e28941d5923" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_dd21600f-3420-48c7-a94d-bf44b8f1f89d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_47dab75b-2399-421b-b314-8e28941d5923" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_9881d606-57cf-48c7-9779-97db1d661eed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_dd21600f-3420-48c7-a94d-bf44b8f1f89d" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_9881d606-57cf-48c7-9779-97db1d661eed" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0b0ffed3-535b-45be-add8-3041ae8bde9f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_9881d606-57cf-48c7-9779-97db1d661eed" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0b0ffed3-535b-45be-add8-3041ae8bde9f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0b0ffed3-535b-45be-add8-3041ae8bde9f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0b0ffed3-535b-45be-add8-3041ae8bde9f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0b0ffed3-535b-45be-add8-3041ae8bde9f_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9e6c7195-1c96-4dce-98a7-2a8ab6c8134a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0b0ffed3-535b-45be-add8-3041ae8bde9f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9e6c7195-1c96-4dce-98a7-2a8ab6c8134a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentedTechnologyMember_2daef5af-8091-4a38-9883-f8a62ebff1ae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PatentedTechnologyMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9e6c7195-1c96-4dce-98a7-2a8ab6c8134a" xlink:to="loc_us-gaap_PatentedTechnologyMember_2daef5af-8091-4a38-9883-f8a62ebff1ae" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_f0f1c9ba-8741-4e1b-ab49-29d452792f44" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerRelationshipsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9e6c7195-1c96-4dce-98a7-2a8ab6c8134a" xlink:to="loc_us-gaap_CustomerRelationshipsMember_f0f1c9ba-8741-4e1b-ab49-29d452792f44" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_d982d4af-195e-4e0b-94e7-4948898c28db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TradeNamesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9e6c7195-1c96-4dce-98a7-2a8ab6c8134a" xlink:to="loc_us-gaap_TradeNamesMember_d982d4af-195e-4e0b-94e7-4948898c28db" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/INTANGIBLEASSETSANDGOODWILLNarrativeDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#INTANGIBLEASSETSANDGOODWILLNarrativeDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/INTANGIBLEASSETSANDGOODWILLNarrativeDetails" xlink:type="extended" id="i8cc39db99d594d578f122e6c885cabc9_INTANGIBLEASSETSANDGOODWILLNarrativeDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b571a368-ae41-4d03-9d6f-863f2bffaa4b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_66ba8203-ab83-4c13-9142-ae4813067f5b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b571a368-ae41-4d03-9d6f-863f2bffaa4b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_66ba8203-ab83-4c13-9142-ae4813067f5b" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_555aa737-164d-41b2-982f-963b23cddb1d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b571a368-ae41-4d03-9d6f-863f2bffaa4b" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_555aa737-164d-41b2-982f-963b23cddb1d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_88008d15-e7da-4089-8ad0-a55617ed62d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_555aa737-164d-41b2-982f-963b23cddb1d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_88008d15-e7da-4089-8ad0-a55617ed62d6" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_88008d15-e7da-4089-8ad0-a55617ed62d6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_88008d15-e7da-4089-8ad0-a55617ed62d6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_88008d15-e7da-4089-8ad0-a55617ed62d6_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae4f7422-05f2-442b-978e-31b98cdc62d2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_88008d15-e7da-4089-8ad0-a55617ed62d6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae4f7422-05f2-442b-978e-31b98cdc62d2" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentedTechnologyMember_0c64bc75-834d-46b3-9709-3b282509582b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PatentedTechnologyMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae4f7422-05f2-442b-978e-31b98cdc62d2" xlink:to="loc_us-gaap_PatentedTechnologyMember_0c64bc75-834d-46b3-9709-3b282509582b" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_dfee2983-500e-461e-a712-5baf2251837d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerRelationshipsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae4f7422-05f2-442b-978e-31b98cdc62d2" xlink:to="loc_us-gaap_CustomerRelationshipsMember_dfee2983-500e-461e-a712-5baf2251837d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_31ceee1b-de39-4b91-9112-a596de47c367" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TradeNamesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ae4f7422-05f2-442b-978e-31b98cdc62d2" xlink:to="loc_us-gaap_TradeNamesMember_31ceee1b-de39-4b91-9112-a596de47c367" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#COMMITMENTSANDCONTINGENCIESDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="extended" id="i423a59b695d84d50af60c3daf28edf54_COMMITMENTSANDCONTINGENCIESDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_c815dd1d-2eab-485c-9ff4-92e80472ec6d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_19c3a1bd-e776-46a4-a6fd-6b4e1b70d398" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_c815dd1d-2eab-485c-9ff4-92e80472ec6d" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_19c3a1bd-e776-46a4-a6fd-6b4e1b70d398" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_1e17320d-4b21-466b-b03b-2a076f436a13" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_c815dd1d-2eab-485c-9ff4-92e80472ec6d" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_1e17320d-4b21-466b-b03b-2a076f436a13" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_187a14ec-ed1d-456a-9362-bcc70d0dd03b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_1e17320d-4b21-466b-b03b-2a076f436a13" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_187a14ec-ed1d-456a-9362-bcc70d0dd03b" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_187a14ec-ed1d-456a-9362-bcc70d0dd03b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossContingencyNatureDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_187a14ec-ed1d-456a-9362-bcc70d0dd03b" xlink:to="loc_us-gaap_LossContingencyNatureDomain_187a14ec-ed1d-456a-9362-bcc70d0dd03b_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_81a6211d-4e0d-49aa-bcfc-f379f30502ca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossContingencyNatureDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_187a14ec-ed1d-456a-9362-bcc70d0dd03b" xlink:to="loc_us-gaap_LossContingencyNatureDomain_81a6211d-4e0d-49aa-bcfc-f379f30502ca" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_StateAndLocalTaxesAndSurchargesMember_95fbb86e-bea5-4b9d-bae3-112a933ecac7" xlink:href="eght-20220630.xsd#eght_StateAndLocalTaxesAndSurchargesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_81a6211d-4e0d-49aa-bcfc-f379f30502ca" xlink:to="loc_eght_StateAndLocalTaxesAndSurchargesMember_95fbb86e-bea5-4b9d-bae3-112a933ecac7" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/CONVERTIBLESENIORNOTESANDCAPPEDCALLSNarrativeDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#CONVERTIBLESENIORNOTESANDCAPPEDCALLSNarrativeDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/CONVERTIBLESENIORNOTESANDCAPPEDCALLSNarrativeDetails" xlink:type="extended" id="id6bd3e5ee2994e9693764c91e2ed41ef_CONVERTIBLESENIORNOTESANDCAPPEDCALLSNarrativeDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_ca6610f6-c7fc-4e59-b766-f9ce4e0c7701" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_ca6610f6-c7fc-4e59-b766-f9ce4e0c7701" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_bce978f4-b5b8-4964-8625-46b3374c02f1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_bce978f4-b5b8-4964-8625-46b3374c02f1" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDebtNetOfIssuanceCosts_d7dac48f-d10b-4e3b-96fb-eac19fa7cd53" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromDebtNetOfIssuanceCosts"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_ProceedsFromDebtNetOfIssuanceCosts_d7dac48f-d10b-4e3b-96fb-eac19fa7cd53" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_88040cac-7905-4b72-be5d-2d8db8038cb0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentConvertibleConversionRatio1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_88040cac-7905-4b72-be5d-2d8db8038cb0" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_b3d582e0-d6cd-4d88-b8d8-8aee7f97bd33" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_b3d582e0-d6cd-4d88-b8d8-8aee7f97bd33" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_f4754fa5-6f28-497d-a9e0-f7ed40e637fd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_f4754fa5-6f28-497d-a9e0-f7ed40e637fd" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_fe7a2739-a77d-4653-a16e-410fa7ead9b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentConvertibleThresholdTradingDays"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdTradingDays_fe7a2739-a77d-4653-a16e-410fa7ead9b7" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_ad3ec24c-f1a6-4e9b-a312-f5bced686e09" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_ad3ec24c-f1a6-4e9b-a312-f5bced686e09" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_0c38e799-db83-4e04-8c6a-e0b361d88233" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_0c38e799-db83-4e04-8c6a-e0b361d88233" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_DebtInstrumentConvertibleMeasurementPeriod_65a0c328-f483-4c03-a756-75fb2c37e219" xlink:href="eght-20220630.xsd#eght_DebtInstrumentConvertibleMeasurementPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_eght_DebtInstrumentConvertibleMeasurementPeriod_65a0c328-f483-4c03-a756-75fb2c37e219" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_DebtInstrumentConvertibleThresholdConsecutiveTradingDaysPrecedingMeasurementPeriod_5146d1de-5f36-4602-ace3-7a9519f5340e" xlink:href="eght-20220630.xsd#eght_DebtInstrumentConvertibleThresholdConsecutiveTradingDaysPrecedingMeasurementPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_eght_DebtInstrumentConvertibleThresholdConsecutiveTradingDaysPrecedingMeasurementPeriod_5146d1de-5f36-4602-ace3-7a9519f5340e" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_DebtInstrumentConvertibleThresholdPercentageOfSalesPrice_b9ed94de-eb94-4fa4-918d-49c1aa19df04" xlink:href="eght-20220630.xsd#eght_DebtInstrumentConvertibleThresholdPercentageOfSalesPrice"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_eght_DebtInstrumentConvertibleThresholdPercentageOfSalesPrice_b9ed94de-eb94-4fa4-918d-49c1aa19df04" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_359668f6-cfa8-4fdb-a8f1-08142d4ec698" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_359668f6-cfa8-4fdb-a8f1-08142d4ec698" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_7270bfb4-35d5-4c68-8348-f168c2e547ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_7270bfb4-35d5-4c68-8348-f168c2e547ec" xlink:type="arc" order="13"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_f00774e3-d6e4-428d-b94e-d4278b0db907" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapital"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_AdditionalPaidInCapital_f00774e3-d6e4-428d-b94e-d4278b0db907" xlink:type="arc" order="14"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_6420a300-1eae-4a85-901a-c81a7a45bd39" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_6420a300-1eae-4a85-901a-c81a7a45bd39" xlink:type="arc" order="15"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1_8651bef7-1125-47bf-8e42-b48abbe0a7a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_DebtInstrumentConvertibleRemainingDiscountAmortizationPeriod1_8651bef7-1125-47bf-8e42-b48abbe0a7a9" xlink:type="arc" order="16"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_fcdfa4fa-7214-45ac-8362-7692cab19bc5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OptionIndexedToIssuersEquityStrikePrice1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityStrikePrice1_fcdfa4fa-7214-45ac-8362-7692cab19bc5" xlink:type="arc" order="17"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_OptionIndexedToIssuersEquityCapPrice_ed974772-8683-4685-85a4-62c994fa0308" xlink:href="eght-20220630.xsd#eght_OptionIndexedToIssuersEquityCapPrice"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_eght_OptionIndexedToIssuersEquityCapPrice_ed974772-8683-4685-85a4-62c994fa0308" xlink:type="arc" order="18"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityIndexedShares_d9501838-eea0-46cf-863f-6230279755b8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OptionIndexedToIssuersEquityIndexedShares"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityIndexedShares_d9501838-eea0-46cf-863f-6230279755b8" xlink:type="arc" order="19"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_77fd264f-d9c6-432f-8f54-31e87448a11d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_01f215bc-72ed-48f2-b7b9-84fa3c108139" xlink:to="loc_us-gaap_DebtInstrumentTable_77fd264f-d9c6-432f-8f54-31e87448a11d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_23e82418-dc04-4f82-90d4-6dea319df778" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_77fd264f-d9c6-432f-8f54-31e87448a11d" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_23e82418-dc04-4f82-90d4-6dea319df778" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_23e82418-dc04-4f82-90d4-6dea319df778_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_23e82418-dc04-4f82-90d4-6dea319df778" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_23e82418-dc04-4f82-90d4-6dea319df778_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_49312ce2-e6b0-47e5-9659-1a4405e67c9a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_23e82418-dc04-4f82-90d4-6dea319df778" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_49312ce2-e6b0-47e5-9659-1a4405e67c9a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_113bfcc9-3c59-4059-8e9a-af4c5dd1a37e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_49312ce2-e6b0-47e5-9659-1a4405e67c9a" xlink:to="loc_us-gaap_ConvertibleDebtMember_113bfcc9-3c59-4059-8e9a-af4c5dd1a37e" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_bfc4a1ab-31ab-4e97-9fa6-b49f996fb899" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_77fd264f-d9c6-432f-8f54-31e87448a11d" xlink:to="loc_us-gaap_DebtInstrumentAxis_bfc4a1ab-31ab-4e97-9fa6-b49f996fb899" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_bfc4a1ab-31ab-4e97-9fa6-b49f996fb899_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_bfc4a1ab-31ab-4e97-9fa6-b49f996fb899" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_bfc4a1ab-31ab-4e97-9fa6-b49f996fb899_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_b136f462-29d7-4ed8-a067-e5f857166079" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_bfc4a1ab-31ab-4e97-9fa6-b49f996fb899" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_b136f462-29d7-4ed8-a067-e5f857166079" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_ConvertibleSeniorNotesMember_6b99c392-0828-4a0e-9e9a-f34a96e4c8ac" xlink:href="eght-20220630.xsd#eght_ConvertibleSeniorNotesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b136f462-29d7-4ed8-a067-e5f857166079" xlink:to="loc_eght_ConvertibleSeniorNotesMember_6b99c392-0828-4a0e-9e9a-f34a96e4c8ac" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_FirstAdditionalNotesMember_6d8d8bb6-2d0f-4ab6-8bec-28f08ed8de74" xlink:href="eght-20220630.xsd#eght_FirstAdditionalNotesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b136f462-29d7-4ed8-a067-e5f857166079" xlink:to="loc_eght_FirstAdditionalNotesMember_6d8d8bb6-2d0f-4ab6-8bec-28f08ed8de74" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_SecondAdditionalNotesMember_183308b6-57b9-41fa-9fe7-6f35d40cd62f" xlink:href="eght-20220630.xsd#eght_SecondAdditionalNotesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b136f462-29d7-4ed8-a067-e5f857166079" xlink:to="loc_eght_SecondAdditionalNotesMember_183308b6-57b9-41fa-9fe7-6f35d40cd62f" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_AggregateNotesMember_26e6b656-cc0e-4ec6-86ef-e0c558e25bab" xlink:href="eght-20220630.xsd#eght_AggregateNotesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_b136f462-29d7-4ed8-a067-e5f857166079" xlink:to="loc_eght_AggregateNotesMember_26e6b656-cc0e-4ec6-86ef-e0c558e25bab" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_436d98eb-c7cb-420d-a842-b60355c800da" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_77fd264f-d9c6-432f-8f54-31e87448a11d" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_436d98eb-c7cb-420d-a842-b60355c800da" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfAdoptionMember_436d98eb-c7cb-420d-a842-b60355c800da_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TypeOfAdoptionMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_436d98eb-c7cb-420d-a842-b60355c800da" xlink:to="loc_us-gaap_TypeOfAdoptionMember_436d98eb-c7cb-420d-a842-b60355c800da_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfAdoptionMember_872c4cde-a7d9-471f-badf-e7c8c12415fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TypeOfAdoptionMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_436d98eb-c7cb-420d-a842-b60355c800da" xlink:to="loc_us-gaap_TypeOfAdoptionMember_872c4cde-a7d9-471f-badf-e7c8c12415fa" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountingStandardsUpdate202006Member_a22d914f-0625-4ab2-862a-df1b73df3b8f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountingStandardsUpdate202006Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_872c4cde-a7d9-471f-badf-e7c8c12415fa" xlink:to="loc_us-gaap_AccountingStandardsUpdate202006Member_a22d914f-0625-4ab2-862a-df1b73df3b8f" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityTypeAxis_d67c2eb6-6b6b-46dd-bf12-5128e228c5e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OptionIndexedToIssuersEquityTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_77fd264f-d9c6-432f-8f54-31e87448a11d" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityTypeAxis_d67c2eb6-6b6b-46dd-bf12-5128e228c5e7" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityTypeDomain_d67c2eb6-6b6b-46dd-bf12-5128e228c5e7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OptionIndexedToIssuersEquityTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OptionIndexedToIssuersEquityTypeAxis_d67c2eb6-6b6b-46dd-bf12-5128e228c5e7" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityTypeDomain_d67c2eb6-6b6b-46dd-bf12-5128e228c5e7_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionIndexedToIssuersEquityTypeDomain_7f8ef515-9577-4224-aa39-3a75a1847025" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OptionIndexedToIssuersEquityTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OptionIndexedToIssuersEquityTypeAxis_d67c2eb6-6b6b-46dd-bf12-5128e228c5e7" xlink:to="loc_us-gaap_OptionIndexedToIssuersEquityTypeDomain_7f8ef515-9577-4224-aa39-3a75a1847025" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CallOptionMember_576aff86-60a1-4f62-8bcd-d77886b5cad7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CallOptionMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OptionIndexedToIssuersEquityTypeDomain_7f8ef515-9577-4224-aa39-3a75a1847025" xlink:to="loc_us-gaap_CallOptionMember_576aff86-60a1-4f62-8bcd-d77886b5cad7" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/CONVERTIBLESENIORNOTESANDCAPPEDCALLSCarryingAmountoftheLiabilityComponentDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#CONVERTIBLESENIORNOTESANDCAPPEDCALLSCarryingAmountoftheLiabilityComponentDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/CONVERTIBLESENIORNOTESANDCAPPEDCALLSCarryingAmountoftheLiabilityComponentDetails" xlink:type="extended" id="i85e0070afa5a4f9da15109012d2d98e4_CONVERTIBLESENIORNOTESANDCAPPEDCALLSCarryingAmountoftheLiabilityComponentDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_2676bd6b-7f39-4f92-b883-6681d173725c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_9e14dfcd-1e05-4a5b-8e6b-ed6dc2f8071f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2676bd6b-7f39-4f92-b883-6681d173725c" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_9e14dfcd-1e05-4a5b-8e6b-ed6dc2f8071f" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_2f37531e-f1ff-4772-940b-7e3ec34ea784" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2676bd6b-7f39-4f92-b883-6681d173725c" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_2f37531e-f1ff-4772-940b-7e3ec34ea784" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_6371a88f-a3c0-4090-bacd-4efb7a0a9bcc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebt"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2676bd6b-7f39-4f92-b883-6681d173725c" xlink:to="loc_us-gaap_LongTermDebt_6371a88f-a3c0-4090-bacd-4efb7a0a9bcc" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_fc11f5e1-7576-4fff-b226-b27a16ec51e8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2676bd6b-7f39-4f92-b883-6681d173725c" xlink:to="loc_us-gaap_DebtInstrumentTable_fc11f5e1-7576-4fff-b226-b27a16ec51e8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_ea96a111-a42d-4e29-bc5e-578239ef68a8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_fc11f5e1-7576-4fff-b226-b27a16ec51e8" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_ea96a111-a42d-4e29-bc5e-578239ef68a8" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ea96a111-a42d-4e29-bc5e-578239ef68a8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ea96a111-a42d-4e29-bc5e-578239ef68a8" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ea96a111-a42d-4e29-bc5e-578239ef68a8_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_f1a831d0-3da3-46bf-83d1-06468ff20099" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ea96a111-a42d-4e29-bc5e-578239ef68a8" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_f1a831d0-3da3-46bf-83d1-06468ff20099" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_b0b2e691-5470-4502-9010-fb9b9de2285e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_f1a831d0-3da3-46bf-83d1-06468ff20099" xlink:to="loc_us-gaap_ConvertibleDebtMember_b0b2e691-5470-4502-9010-fb9b9de2285e" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_da368b4d-e20b-41dd-a68f-5ddf43878351" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_fc11f5e1-7576-4fff-b226-b27a16ec51e8" xlink:to="loc_us-gaap_DebtInstrumentAxis_da368b4d-e20b-41dd-a68f-5ddf43878351" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_da368b4d-e20b-41dd-a68f-5ddf43878351_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_da368b4d-e20b-41dd-a68f-5ddf43878351" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_da368b4d-e20b-41dd-a68f-5ddf43878351_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_3a9880a8-bd44-4079-b002-392348f62ef7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_da368b4d-e20b-41dd-a68f-5ddf43878351" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_3a9880a8-bd44-4079-b002-392348f62ef7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_ConvertibleSeniorNotesMember_8d7021c0-ec70-4495-8f79-058f4a310eba" xlink:href="eght-20220630.xsd#eght_ConvertibleSeniorNotesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3a9880a8-bd44-4079-b002-392348f62ef7" xlink:to="loc_eght_ConvertibleSeniorNotesMember_8d7021c0-ec70-4495-8f79-058f4a310eba" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/CONVERTIBLESENIORNOTESANDCAPPEDCALLSInterestExpenseDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#CONVERTIBLESENIORNOTESANDCAPPEDCALLSInterestExpenseDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/CONVERTIBLESENIORNOTESANDCAPPEDCALLSInterestExpenseDetails" xlink:type="extended" id="idba172c40baf47eca0401b20404e0176_CONVERTIBLESENIORNOTESANDCAPPEDCALLSInterestExpenseDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_1a5426ba-9587-467d-b462-6727cbdaec6a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebtExcludingAmortization_119556a7-86d6-48f6-aba6-bf64b4055d23" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpenseDebtExcludingAmortization"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1a5426ba-9587-467d-b462-6727cbdaec6a" xlink:to="loc_us-gaap_InterestExpenseDebtExcludingAmortization_119556a7-86d6-48f6-aba6-bf64b4055d23" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_c8659f7a-a672-4c1f-ba25-61ebaf545a9d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1a5426ba-9587-467d-b462-6727cbdaec6a" xlink:to="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_c8659f7a-a672-4c1f-ba25-61ebaf545a9d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_e688cafa-9ce2-4225-b6b4-f3574c17a5bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpenseDebt"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1a5426ba-9587-467d-b462-6727cbdaec6a" xlink:to="loc_us-gaap_InterestExpenseDebt_e688cafa-9ce2-4225-b6b4-f3574c17a5bc" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_f05c2c89-760f-4f65-853b-d7023d44c8a4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_1a5426ba-9587-467d-b462-6727cbdaec6a" xlink:to="loc_us-gaap_DebtInstrumentTable_f05c2c89-760f-4f65-853b-d7023d44c8a4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_a84c2d1d-2b2a-43c4-a91d-14b8405920bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f05c2c89-760f-4f65-853b-d7023d44c8a4" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_a84c2d1d-2b2a-43c4-a91d-14b8405920bc" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a84c2d1d-2b2a-43c4-a91d-14b8405920bc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a84c2d1d-2b2a-43c4-a91d-14b8405920bc" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a84c2d1d-2b2a-43c4-a91d-14b8405920bc_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0bd84b80-2346-4067-924d-84783183c037" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a84c2d1d-2b2a-43c4-a91d-14b8405920bc" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0bd84b80-2346-4067-924d-84783183c037" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_82b7df3e-c3cb-4f66-b531-3c95e71cd4b5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConvertibleDebtMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_0bd84b80-2346-4067-924d-84783183c037" xlink:to="loc_us-gaap_ConvertibleDebtMember_82b7df3e-c3cb-4f66-b531-3c95e71cd4b5" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_270ec2c5-6562-4d3d-a8c9-9ea5182073ad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f05c2c89-760f-4f65-853b-d7023d44c8a4" xlink:to="loc_us-gaap_DebtInstrumentAxis_270ec2c5-6562-4d3d-a8c9-9ea5182073ad" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_270ec2c5-6562-4d3d-a8c9-9ea5182073ad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_270ec2c5-6562-4d3d-a8c9-9ea5182073ad" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_270ec2c5-6562-4d3d-a8c9-9ea5182073ad_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1c38633b-e380-4661-b3ca-f3059476e10a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_270ec2c5-6562-4d3d-a8c9-9ea5182073ad" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1c38633b-e380-4661-b3ca-f3059476e10a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_ConvertibleSeniorNotesMember_7727fd63-2cf7-4652-9051-e672c8823d93" xlink:href="eght-20220630.xsd#eght_ConvertibleSeniorNotesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1c38633b-e380-4661-b3ca-f3059476e10a" xlink:to="loc_eght_ConvertibleSeniorNotesMember_7727fd63-2cf7-4652-9051-e672c8823d93" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYNarrativeDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYNarrativeDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYNarrativeDetails" xlink:type="extended" id="i77f831c408af409eb4dfa63a5c802a7f_STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYNarrativeDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_77b0d8e1-6336-4cd5-a330-87dd7a80af07" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_77b0d8e1-6336-4cd5-a330-87dd7a80af07" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_CommonStockAdditionalCapitalSharesReservedforFutureIssuance_a9486b40-cb6e-45e7-ab76-d83f9a05b77a" xlink:href="eght-20220630.xsd#eght_CommonStockAdditionalCapitalSharesReservedforFutureIssuance"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_eght_CommonStockAdditionalCapitalSharesReservedforFutureIssuance_a9486b40-cb6e-45e7-ab76-d83f9a05b77a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_d88877ae-8084-40c1-8c41-05bad3ed1190" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_d88877ae-8084-40c1-8c41-05bad3ed1190" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_ca6fbfad-5850-42b2-8b88-3a399d2cc414" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_ca6fbfad-5850-42b2-8b88-3a399d2cc414" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_39cbcac4-0ff4-4bb4-99e3-579f6107f222" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_39cbcac4-0ff4-4bb4-99e3-579f6107f222" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_3857d0be-5763-4ad8-b06b-898230603c2f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_3857d0be-5763-4ad8-b06b-898230603c2f" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_c9b6bb87-6df8-44b1-ab1d-4d9591848a17" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_c9b6bb87-6df8-44b1-ab1d-4d9591848a17" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_79600db7-696c-435d-9fda-0d70662790f8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_79600db7-696c-435d-9fda-0d70662790f8" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod_c6c81f71-174f-4da2-af00-9d2a6651bb33" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod_c6c81f71-174f-4da2-af00-9d2a6651bb33" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentageChangeInSharesEarned_a75b6b92-1b9f-4b26-8759-edea5e41203e" xlink:href="eght-20220630.xsd#eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentageChangeInSharesEarned"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsPercentageChangeInSharesEarned_a75b6b92-1b9f-4b26-8759-edea5e41203e" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsMaximumPercentageOfSharesToBeEarned_3bd9d282-ac36-48a3-87d8-bef0e6265f12" xlink:href="eght-20220630.xsd#eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsMaximumPercentageOfSharesToBeEarned"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRightsMaximumPercentageOfSharesToBeEarned_3bd9d282-ac36-48a3-87d8-bef0e6265f12" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardTotalShareholderReturnPerformanceLowestPercentageToStillEarnAwards_2ba3995d-878d-4557-b37e-3bcea8372abf" xlink:href="eght-20220630.xsd#eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardTotalShareholderReturnPerformanceLowestPercentageToStillEarnAwards"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardTotalShareholderReturnPerformanceLowestPercentageToStillEarnAwards_2ba3995d-878d-4557-b37e-3bcea8372abf" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_ad6df5f7-46f0-465b-b2bd-108caf11da0c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_ad6df5f7-46f0-465b-b2bd-108caf11da0c" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_2affc1e8-26bb-4036-bc1c-72c3accc1894" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TreasuryStockSharesAcquired"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_2affc1e8-26bb-4036-bc1c-72c3accc1894" xlink:type="arc" order="13"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_18b72344-4ee7-4093-b82b-9889a46aad58" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_31600169-8556-471d-bb22-fe2e2aa83cdb" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_18b72344-4ee7-4093-b82b-9889a46aad58" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_e77a78c2-37ef-47f7-bd3b-0d673b24ade5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_18b72344-4ee7-4093-b82b-9889a46aad58" xlink:to="loc_us-gaap_PlanNameAxis_e77a78c2-37ef-47f7-bd3b-0d673b24ade5" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_e77a78c2-37ef-47f7-bd3b-0d673b24ade5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_e77a78c2-37ef-47f7-bd3b-0d673b24ade5" xlink:to="loc_us-gaap_PlanNameDomain_e77a78c2-37ef-47f7-bd3b-0d673b24ade5_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_d8d05c1a-01bf-4c27-a407-f52d6237cea2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_e77a78c2-37ef-47f7-bd3b-0d673b24ade5" xlink:to="loc_us-gaap_PlanNameDomain_d8d05c1a-01bf-4c27-a407-f52d6237cea2" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_A2012PlanMember_3d576224-b64c-4dc8-b6c3-0ff4f343433a" xlink:href="eght-20220630.xsd#eght_A2012PlanMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_d8d05c1a-01bf-4c27-a407-f52d6237cea2" xlink:to="loc_eght_A2012PlanMember_3d576224-b64c-4dc8-b6c3-0ff4f343433a" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_A2017PlanMember_d8439501-1503-4ce2-b334-ebd8c5f7ad29" xlink:href="eght-20220630.xsd#eght_A2017PlanMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_d8d05c1a-01bf-4c27-a407-f52d6237cea2" xlink:to="loc_eght_A2017PlanMember_d8439501-1503-4ce2-b334-ebd8c5f7ad29" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_EmployeeStockPurchasePlanMember_b806bf02-0891-4bd3-819f-c90c28187f99" xlink:href="eght-20220630.xsd#eght_EmployeeStockPurchasePlanMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_d8d05c1a-01bf-4c27-a407-f52d6237cea2" xlink:to="loc_eght_EmployeeStockPurchasePlanMember_b806bf02-0891-4bd3-819f-c90c28187f99" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_5a601b77-b8b4-496c-92a1-fcad9d57980a" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_18b72344-4ee7-4093-b82b-9889a46aad58" xlink:to="loc_srt_RangeAxis_5a601b77-b8b4-496c-92a1-fcad9d57980a" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5a601b77-b8b4-496c-92a1-fcad9d57980a_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_5a601b77-b8b4-496c-92a1-fcad9d57980a" xlink:to="loc_srt_RangeMember_5a601b77-b8b4-496c-92a1-fcad9d57980a_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_36733f74-4a8a-4065-9f29-6ea8e362500c" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_5a601b77-b8b4-496c-92a1-fcad9d57980a" xlink:to="loc_srt_RangeMember_36733f74-4a8a-4065-9f29-6ea8e362500c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_5c6e9cb9-2264-4a72-9a2c-ff84599b0aa4" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_36733f74-4a8a-4065-9f29-6ea8e362500c" xlink:to="loc_srt_MinimumMember_5c6e9cb9-2264-4a72-9a2c-ff84599b0aa4" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_21c6b5f7-9c40-49e4-8923-44b050bc5442" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_36733f74-4a8a-4065-9f29-6ea8e362500c" xlink:to="loc_srt_MaximumMember_21c6b5f7-9c40-49e4-8923-44b050bc5442" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_e0bfa4c9-2f13-4ac5-8841-a5ef53575c8a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_18b72344-4ee7-4093-b82b-9889a46aad58" xlink:to="loc_us-gaap_AwardTypeAxis_e0bfa4c9-2f13-4ac5-8841-a5ef53575c8a" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e0bfa4c9-2f13-4ac5-8841-a5ef53575c8a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_e0bfa4c9-2f13-4ac5-8841-a5ef53575c8a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e0bfa4c9-2f13-4ac5-8841-a5ef53575c8a_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_08034439-cd7e-4ad7-a2ef-940a95f55105" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_e0bfa4c9-2f13-4ac5-8841-a5ef53575c8a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_08034439-cd7e-4ad7-a2ef-940a95f55105" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_6be7c6f4-e748-4e4a-b876-a560edb1a80b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_08034439-cd7e-4ad7-a2ef-940a95f55105" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_6be7c6f4-e748-4e4a-b876-a560edb1a80b" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_e45c13d7-90b6-4985-9e0a-eaa1592b02ab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockOptionMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_08034439-cd7e-4ad7-a2ef-940a95f55105" xlink:to="loc_us-gaap_EmployeeStockOptionMember_e45c13d7-90b6-4985-9e0a-eaa1592b02ab" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_StockPurchaseRightMember_47d74195-ab15-4da5-9845-3dcbab8439b4" xlink:href="eght-20220630.xsd#eght_StockPurchaseRightMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_08034439-cd7e-4ad7-a2ef-940a95f55105" xlink:to="loc_eght_StockPurchaseRightMember_47d74195-ab15-4da5-9845-3dcbab8439b4" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_e8e49cd9-87d6-4701-9cc6-72bf1e729d68" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PerformanceSharesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_08034439-cd7e-4ad7-a2ef-940a95f55105" xlink:to="loc_us-gaap_PerformanceSharesMember_e8e49cd9-87d6-4701-9cc6-72bf1e729d68" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_87276f46-28e0-4672-9711-b7b3b9bfa089" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_08034439-cd7e-4ad7-a2ef-940a95f55105" xlink:to="loc_us-gaap_EmployeeStockMember_87276f46-28e0-4672-9711-b7b3b9bfa089" xlink:type="arc" order="4"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYStockBasedCompensationExpenseByStatementOfOperationsDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYStockBasedCompensationExpenseByStatementOfOperationsDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYStockBasedCompensationExpenseByStatementOfOperationsDetails" xlink:type="extended" id="i29a8f675bd2e43d2ab027c9d133e1447_STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYStockBasedCompensationExpenseByStatementOfOperationsDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_66d28671-dd6f-4d9c-bb87-5173cadf37c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax_34f1658a-3d23-4f68-8262-5b2660e4d271" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_66d28671-dd6f-4d9c-bb87-5173cadf37c2" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax_34f1658a-3d23-4f68-8262-5b2660e4d271" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_465f91b2-be90-40ad-80a6-6dd39a6ed58d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_66d28671-dd6f-4d9c-bb87-5173cadf37c2" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_465f91b2-be90-40ad-80a6-6dd39a6ed58d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_034cee1e-5491-4e83-82a6-cd18738014a6" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_465f91b2-be90-40ad-80a6-6dd39a6ed58d" xlink:to="loc_srt_ProductOrServiceAxis_034cee1e-5491-4e83-82a6-cd18738014a6" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_034cee1e-5491-4e83-82a6-cd18738014a6_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_034cee1e-5491-4e83-82a6-cd18738014a6" xlink:to="loc_srt_ProductsAndServicesDomain_034cee1e-5491-4e83-82a6-cd18738014a6_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d7c80a46-b7ed-4fa5-9af5-9536ac35bbbe" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_034cee1e-5491-4e83-82a6-cd18738014a6" xlink:to="loc_srt_ProductsAndServicesDomain_d7c80a46-b7ed-4fa5-9af5-9536ac35bbbe" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceMember_2b9b3cb4-c11a-4c60-adae-af235c221ed6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ServiceMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d7c80a46-b7ed-4fa5-9af5-9536ac35bbbe" xlink:to="loc_us-gaap_ServiceMember_2b9b3cb4-c11a-4c60-adae-af235c221ed6" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_1abeb768-f8eb-4620-a40e-1c1fe1915116" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProductAndServiceOtherMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d7c80a46-b7ed-4fa5-9af5-9536ac35bbbe" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_1abeb768-f8eb-4620-a40e-1c1fe1915116" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_b0c594df-35bf-43be-b034-9ccf3efe2377" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_465f91b2-be90-40ad-80a6-6dd39a6ed58d" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_b0c594df-35bf-43be-b034-9ccf3efe2377" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_b0c594df-35bf-43be-b034-9ccf3efe2377_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_b0c594df-35bf-43be-b034-9ccf3efe2377" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_b0c594df-35bf-43be-b034-9ccf3efe2377_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_c2e66daa-273f-414d-9988-b67d7109949f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_b0c594df-35bf-43be-b034-9ccf3efe2377" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_c2e66daa-273f-414d-9988-b67d7109949f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_357cab43-9a8e-46b5-85c2-8df130e35bc8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CostOfSalesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_c2e66daa-273f-414d-9988-b67d7109949f" xlink:to="loc_us-gaap_CostOfSalesMember_357cab43-9a8e-46b5-85c2-8df130e35bc8" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_b9e2f355-12dc-467f-89bb-4d4576d20d19" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_c2e66daa-273f-414d-9988-b67d7109949f" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_b9e2f355-12dc-467f-89bb-4d4576d20d19" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_920518aa-b0c0-4e39-8c07-4516637ea09d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SellingAndMarketingExpenseMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_c2e66daa-273f-414d-9988-b67d7109949f" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_920518aa-b0c0-4e39-8c07-4516637ea09d" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_5cbfa176-d8fc-4c07-8752-75e1228ea55f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_c2e66daa-273f-414d-9988-b67d7109949f" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_5cbfa176-d8fc-4c07-8752-75e1228ea55f" xlink:type="arc" order="3"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYSTOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYRestrictedStockUnitandPerformanceStockUnitActivityDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYSTOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYRestrictedStockUnitandPerformanceStockUnitActivityDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYSTOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYRestrictedStockUnitandPerformanceStockUnitActivityDetails" xlink:type="extended" id="i1887ad9a538c492bbdff7ca3e9e6e103_STOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYSTOCKBASEDCOMPENSATIONANDSTOCKHOLDERSEQUITYRestrictedStockUnitandPerformanceStockUnitActivityDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e5f40324-576c-4456-afce-dfc764e19192" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_4c588850-e372-435c-bb49-36abf7cc6318" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e5f40324-576c-4456-afce-dfc764e19192" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_4c588850-e372-435c-bb49-36abf7cc6318" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_7680a7fb-d115-4257-a4bb-a9f2bc3f1210" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_4c588850-e372-435c-bb49-36abf7cc6318" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_7680a7fb-d115-4257-a4bb-a9f2bc3f1210" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_f2a75cde-2713-470d-8839-61e7ff9d8f98" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_4c588850-e372-435c-bb49-36abf7cc6318" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_f2a75cde-2713-470d-8839-61e7ff9d8f98" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAchievementInPeriod_8a654872-9a7a-44a6-b1cf-3a09a1f4600e" xlink:href="eght-20220630.xsd#eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAchievementInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_4c588850-e372-435c-bb49-36abf7cc6318" xlink:to="loc_eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAchievementInPeriod_8a654872-9a7a-44a6-b1cf-3a09a1f4600e" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_deb8f9a0-cde8-435e-a68f-f60ebb41b5ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_4c588850-e372-435c-bb49-36abf7cc6318" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_deb8f9a0-cde8-435e-a68f-f60ebb41b5ec" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_7ee68485-1cc4-4e3a-95d0-8620644df2f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_4c588850-e372-435c-bb49-36abf7cc6318" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_7ee68485-1cc4-4e3a-95d0-8620644df2f9" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_f7fd49f0-d480-46cc-bf89-0a6f0bad596f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_ee24e8a1-084c-461e-a018-0ea57e345073" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e5f40324-576c-4456-afce-dfc764e19192" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_ee24e8a1-084c-461e-a018-0ea57e345073" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_701ea08c-fccd-4fdd-be0c-c7a92d071fce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_ee24e8a1-084c-461e-a018-0ea57e345073" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_701ea08c-fccd-4fdd-be0c-c7a92d071fce" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_3ce8cbdb-d819-4e5a-93f0-4baacd335791" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_ee24e8a1-084c-461e-a018-0ea57e345073" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_3ce8cbdb-d819-4e5a-93f0-4baacd335791" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAchievementInPeriodWeightedAverageGrantDateFairValue_6d475947-459a-4a87-8f00-a242eb73fe38" xlink:href="eght-20220630.xsd#eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAchievementInPeriodWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_ee24e8a1-084c-461e-a018-0ea57e345073" xlink:to="loc_eght_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceAchievementInPeriodWeightedAverageGrantDateFairValue_6d475947-459a-4a87-8f00-a242eb73fe38" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_3d3957f9-2a24-45e7-afb0-db04889a987e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_ee24e8a1-084c-461e-a018-0ea57e345073" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_3d3957f9-2a24-45e7-afb0-db04889a987e" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_e8a35551-b326-496b-a7e5-b32388fe349f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_ee24e8a1-084c-461e-a018-0ea57e345073" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_e8a35551-b326-496b-a7e5-b32388fe349f" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_1df5dc22-a61f-4c9d-8ef6-0aadca704376" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_77709520-c2e5-4c1c-9a10-85a9e28b1ab7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e5f40324-576c-4456-afce-dfc764e19192" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_77709520-c2e5-4c1c-9a10-85a9e28b1ab7" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8b81852f-854a-4d50-83d0-30eb0d6d4b8c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e5f40324-576c-4456-afce-dfc764e19192" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8b81852f-854a-4d50-83d0-30eb0d6d4b8c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_2e28deb9-a40e-4662-a0e8-8dcf71f09227" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8b81852f-854a-4d50-83d0-30eb0d6d4b8c" xlink:to="loc_us-gaap_AwardTypeAxis_2e28deb9-a40e-4662-a0e8-8dcf71f09227" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2e28deb9-a40e-4662-a0e8-8dcf71f09227_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_2e28deb9-a40e-4662-a0e8-8dcf71f09227" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2e28deb9-a40e-4662-a0e8-8dcf71f09227_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a6d8886d-a382-4989-8d46-4a811aa43bdb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_2e28deb9-a40e-4662-a0e8-8dcf71f09227" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a6d8886d-a382-4989-8d46-4a811aa43bdb" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_b13b2965-373b-4cb1-96e7-5ab7077ce7e1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a6d8886d-a382-4989-8d46-4a811aa43bdb" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_b13b2965-373b-4cb1-96e7-5ab7077ce7e1" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_02ca6bbc-2bb8-4260-9b0d-4e22686af153" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PerformanceSharesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a6d8886d-a382-4989-8d46-4a811aa43bdb" xlink:to="loc_us-gaap_PerformanceSharesMember_02ca6bbc-2bb8-4260-9b0d-4e22686af153" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/NETLOSSPERSHAREScheduleofAntidilutiveAwardsDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#NETLOSSPERSHAREScheduleofAntidilutiveAwardsDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/NETLOSSPERSHAREScheduleofAntidilutiveAwardsDetails" xlink:type="extended" id="i06f21da6c0f34b169b804be4aa0affe1_NETLOSSPERSHAREScheduleofAntidilutiveAwardsDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_276ec5cb-2497-420b-a027-9a0ac2d88cde" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_653ad676-17b0-4476-9d69-6d6a6319e536" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_276ec5cb-2497-420b-a027-9a0ac2d88cde" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_653ad676-17b0-4476-9d69-6d6a6319e536" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_45182c15-65fa-4f3c-a430-b23c7ba36117" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_276ec5cb-2497-420b-a027-9a0ac2d88cde" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_45182c15-65fa-4f3c-a430-b23c7ba36117" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_30cd7881-d822-4321-8ae9-8ba681c5a588" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_45182c15-65fa-4f3c-a430-b23c7ba36117" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_30cd7881-d822-4321-8ae9-8ba681c5a588" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_30cd7881-d822-4321-8ae9-8ba681c5a588_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_30cd7881-d822-4321-8ae9-8ba681c5a588" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_30cd7881-d822-4321-8ae9-8ba681c5a588_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_b6e677e6-dfc5-4078-aaed-7bc16aaf9434" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_30cd7881-d822-4321-8ae9-8ba681c5a588" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_b6e677e6-dfc5-4078-aaed-7bc16aaf9434" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_8fdb7e87-9eac-454b-9469-862a2fd3d292" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockOptionMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_b6e677e6-dfc5-4078-aaed-7bc16aaf9434" xlink:to="loc_us-gaap_EmployeeStockOptionMember_8fdb7e87-9eac-454b-9469-862a2fd3d292" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_RestrictedStockUnitsAndPerformanceSharesMember_9e3c12ea-64b7-43ad-a68c-a5ddcdd47f03" xlink:href="eght-20220630.xsd#eght_RestrictedStockUnitsAndPerformanceSharesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_b6e677e6-dfc5-4078-aaed-7bc16aaf9434" xlink:to="loc_eght_RestrictedStockUnitsAndPerformanceSharesMember_9e3c12ea-64b7-43ad-a68c-a5ddcdd47f03" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_SharesIssuedUnderEmployeeStockPurchasePlanMember_a280b8fc-a9ce-4d1d-9457-eb84806786d9" xlink:href="eght-20220630.xsd#eght_SharesIssuedUnderEmployeeStockPurchasePlanMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_b6e677e6-dfc5-4078-aaed-7bc16aaf9434" xlink:to="loc_eght_SharesIssuedUnderEmployeeStockPurchasePlanMember_a280b8fc-a9ce-4d1d-9457-eb84806786d9" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/GEOGRAPHICALINFORMATIONDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#GEOGRAPHICALINFORMATIONDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/GEOGRAPHICALINFORMATIONDetails" xlink:type="extended" id="ied7244cc6e574bae87edcc04962e469f_GEOGRAPHICALINFORMATIONDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_174e45ed-5a3d-4c54-b027-beb9999a63cd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentReportingInformationLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_aa904089-c3fd-4de7-9192-7845150499fe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_174e45ed-5a3d-4c54-b027-beb9999a63cd" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_aa904089-c3fd-4de7-9192-7845150499fe" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_06e948a9-c786-42d9-940d-580b2d108fe7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_174e45ed-5a3d-4c54-b027-beb9999a63cd" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_06e948a9-c786-42d9-940d-580b2d108fe7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8e8b5a2a-4f3a-4eda-868c-c5f249bec083" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_174e45ed-5a3d-4c54-b027-beb9999a63cd" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8e8b5a2a-4f3a-4eda-868c-c5f249bec083" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_a45152c2-ab26-4fb8-bccb-69e51c4611ba" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_StatementGeographicalAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8e8b5a2a-4f3a-4eda-868c-c5f249bec083" xlink:to="loc_srt_StatementGeographicalAxis_a45152c2-ab26-4fb8-bccb-69e51c4611ba" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_a45152c2-ab26-4fb8-bccb-69e51c4611ba_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_a45152c2-ab26-4fb8-bccb-69e51c4611ba" xlink:to="loc_srt_SegmentGeographicalDomain_a45152c2-ab26-4fb8-bccb-69e51c4611ba_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_4ed7073b-f60b-41bf-a4a4-2ab13a50759f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_a45152c2-ab26-4fb8-bccb-69e51c4611ba" xlink:to="loc_srt_SegmentGeographicalDomain_4ed7073b-f60b-41bf-a4a4-2ab13a50759f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_country_US_1588f34e-ae2a-4185-a34e-bcd319cafefb" xlink:href="https://xbrl.sec.gov/country/2022/country-2022.xsd#country_US"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_4ed7073b-f60b-41bf-a4a4-2ab13a50759f" xlink:to="loc_country_US_1588f34e-ae2a-4185-a34e-bcd319cafefb" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_e10e877a-e2e6-4790-b5ef-fa27745905ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NonUsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_4ed7073b-f60b-41bf-a4a4-2ab13a50759f" xlink:to="loc_us-gaap_NonUsMember_e10e877a-e2e6-4790-b5ef-fa27745905ec" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://8x8.com/role/ACQUISITIONSNarrativeDetails" xlink:type="simple" xlink:href="eght-20220630.xsd#ACQUISITIONSNarrativeDetails"/>
<link:definitionLink xlink:role="http://8x8.com/role/ACQUISITIONSNarrativeDetails" xlink:type="extended" id="ibebc32fd9e8d481b912ce1e59089ebb1_ACQUISITIONSNarrativeDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_6d3317f8-a0f4-47f3-8f87-682ecf2e42d1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_bf6aae38-51bd-4605-9838-fe47a5dfc25e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6d3317f8-a0f4-47f3-8f87-682ecf2e42d1" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_bf6aae38-51bd-4605-9838-fe47a5dfc25e" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_0a178490-b298-4eff-803a-048b053a9ec8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6d3317f8-a0f4-47f3-8f87-682ecf2e42d1" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_0a178490-b298-4eff-803a-048b053a9ec8" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_7628d56c-45bf-4675-941d-da042842be11" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6d3317f8-a0f4-47f3-8f87-682ecf2e42d1" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_7628d56c-45bf-4675-941d-da042842be11" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_c4fb5205-c10e-44f9-8a92-def4b51819cf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6d3317f8-a0f4-47f3-8f87-682ecf2e42d1" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_c4fb5205-c10e-44f9-8a92-def4b51819cf" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_BusinessCombinationConsiderationTransferredCashHeldBack_40447389-2d26-45b0-a2be-d5b715013b37" xlink:href="eght-20220630.xsd#eght_BusinessCombinationConsiderationTransferredCashHeldBack"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6d3317f8-a0f4-47f3-8f87-682ecf2e42d1" xlink:to="loc_eght_BusinessCombinationConsiderationTransferredCashHeldBack_40447389-2d26-45b0-a2be-d5b715013b37" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableHeldBack_9c55fe46-f7ad-4891-bc30-4e46030a087b" xlink:href="eght-20220630.xsd#eght_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableHeldBack"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6d3317f8-a0f4-47f3-8f87-682ecf2e42d1" xlink:to="loc_eght_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableHeldBack_9c55fe46-f7ad-4891-bc30-4e46030a087b" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableSharesHeldBackForIndemnityObligations_282b7411-d62b-4ab8-bbe8-3a027d16c19e" xlink:href="eght-20220630.xsd#eght_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableSharesHeldBackForIndemnityObligations"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6d3317f8-a0f4-47f3-8f87-682ecf2e42d1" xlink:to="loc_eght_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableSharesHeldBackForIndemnityObligations_282b7411-d62b-4ab8-bbe8-3a027d16c19e" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_3f42570e-8ec9-4100-9e68-0b336e2db966" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6d3317f8-a0f4-47f3-8f87-682ecf2e42d1" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_3f42570e-8ec9-4100-9e68-0b336e2db966" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b886e4be-1450-4023-95da-2ce041e1fde7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6d3317f8-a0f4-47f3-8f87-682ecf2e42d1" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b886e4be-1450-4023-95da-2ce041e1fde7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_cae748a5-5bf4-4bd3-b005-db49ff02e64b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b886e4be-1450-4023-95da-2ce041e1fde7" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_cae748a5-5bf4-4bd3-b005-db49ff02e64b" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cae748a5-5bf4-4bd3-b005-db49ff02e64b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_cae748a5-5bf4-4bd3-b005-db49ff02e64b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cae748a5-5bf4-4bd3-b005-db49ff02e64b_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ba5e3f04-3605-46b3-a372-d5117a6ed7c5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_cae748a5-5bf4-4bd3-b005-db49ff02e64b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ba5e3f04-3605-46b3-a372-d5117a6ed7c5" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_eght_FuzeMember_a13a85fe-b96e-492f-898b-b759de5fa8f8" xlink:href="eght-20220630.xsd#eght_FuzeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ba5e3f04-3605-46b3-a372-d5117a6ed7c5" xlink:to="loc_eght_FuzeMember_a13a85fe-b96e-492f-898b-b759de5fa8f8" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_60a03196-68ea-4ba4-b456-4ef1121d72ca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_b886e4be-1450-4023-95da-2ce041e1fde7" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_60a03196-68ea-4ba4-b456-4ef1121d72ca" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_60a03196-68ea-4ba4-b456-4ef1121d72ca_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_60a03196-68ea-4ba4-b456-4ef1121d72ca" xlink:to="loc_us-gaap_EquityComponentDomain_60a03196-68ea-4ba4-b456-4ef1121d72ca_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_17c6ea4c-ca07-4df1-a682-5e7221f42be9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_60a03196-68ea-4ba4-b456-4ef1121d72ca" xlink:to="loc_us-gaap_EquityComponentDomain_17c6ea4c-ca07-4df1-a682-5e7221f42be9" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_9704823c-3d8e-4653-9c00-ae1eb9143dcd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_17c6ea4c-ca07-4df1-a682-5e7221f42be9" xlink:to="loc_us-gaap_CommonStockMember_9704823c-3d8e-4653-9c00-ae1eb9143dcd" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-roles-2022.xsd#eedm"/>
<link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfAdoptionMember" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TypeOfAdoptionMember"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountingStandardsUpdate202006Member" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountingStandardsUpdate202006Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember" xlink:to="loc_us-gaap_AccountingStandardsUpdate202006Member" xlink:type="arc" order="0"/>
</link:definitionLink>
</link:linkbase>


2 Previous Filings that this Filing References

  As Of               Filer                 Filing    For·On·As Docs:Size             Issuer                      Filing Agent

 7/13/22  8X8 Inc./DE                       8-K:5       7/12/22   11:828K
 7/29/15  8X8 Inc./DE                       8-K:5,9     7/23/15    2:138K                                   Meyer Harol… Gretchen/FA
Top
Filing Submission 0001023731-22-000169   –   Alternative Formats (Word / Rich Text, HTML, Plain Text, et al.)

Copyright © 2024 Fran Finnegan & Company LLC – All Rights Reserved.
AboutPrivacyRedactionsHelp — Tue., May 14, 7:21:29.1am ET