<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019eb20b-d9da-7287-a3bb-d710290b4e05,g:f26436a3-e3b9-44c7-a8de-624f3eb4a384-->
<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://www.novocure.com/role/CONSOLIDATEDSTATEMENTSOFCHANGESINSHAREHOLDERSEQUITY" xlink:type="simple" xlink:href="nvcr-20260630.xsd#CONSOLIDATEDSTATEMENTSOFCHANGESINSHAREHOLDERSEQUITY"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/CONSOLIDATEDSTATEMENTSOFCHANGESINSHAREHOLDERSEQUITY" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019eb20b-da8e-7916-afa9-53a0fa615054" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019eb20b-da8e-713a-83bd-0ec027b9cb42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019eb20b-da8e-7916-afa9-53a0fa615054" xlink:to="loc_us-gaap_StatementTable_019eb20b-da8e-713a-83bd-0ec027b9cb42" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019eb20b-da8e-7719-91d5-d479027ba767" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019eb20b-da8e-713a-83bd-0ec027b9cb42" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019eb20b-da8e-7719-91d5-d479027ba767" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb20b-da8e-7719-91d5-d479027ba767_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb20b-da8e-7719-91d5-d479027ba767" xlink:to="loc_us-gaap_EquityComponentDomain_019eb20b-da8e-7719-91d5-d479027ba767_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019eb20b-da8e-7d8e-8dac-a14e5b2b1870" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019eb20b-da8e-7719-91d5-d479027ba767" xlink:to="loc_us-gaap_EquityComponentDomain_019eb20b-da8e-7d8e-8dac-a14e5b2b1870" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019eb20b-da8e-7400-bc1d-cce77bb977a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019eb20b-da8e-7d8e-8dac-a14e5b2b1870" xlink:to="loc_us-gaap_CommonStockMember_019eb20b-da8e-7400-bc1d-cce77bb977a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019eb20b-da8e-7faa-afc6-661141934f73" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019eb20b-da8e-7d8e-8dac-a14e5b2b1870" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019eb20b-da8e-7faa-afc6-661141934f73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb20b-da8e-7e83-a16d-666cfa93b8ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019eb20b-da8e-7d8e-8dac-a14e5b2b1870" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019eb20b-da8e-7e83-a16d-666cfa93b8ef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019eb20b-da8e-7678-8890-4115540090ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019eb20b-da8e-7d8e-8dac-a14e5b2b1870" xlink:to="loc_us-gaap_RetainedEarningsMember_019eb20b-da8e-7678-8890-4115540090ab" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019eb20b-da8e-7916-afa9-53a0fa615054" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_019eb20b-da8e-7db9-99d5-81eae2c91996" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:to="loc_us-gaap_SharesOutstanding_019eb20b-da8e-7db9-99d5-81eae2c91996" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019eb20b-da8e-797f-adf6-58348b610e44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:to="loc_us-gaap_StockholdersEquity_019eb20b-da8e-797f-adf6-58348b610e44" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019eb20b-da8e-7e43-abbf-419ca22df17d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019eb20b-da8e-7e43-abbf-419ca22df17d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019f4b17-d0f3-7aae-b3c0-ee1c1df84303" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019f4b17-d0f3-7aae-b3c0-ee1c1df84303" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019f4b17-d0f3-7ef0-afbe-71cff75b86b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019f4b17-d0f3-7ef0-afbe-71cff75b86b0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_StockIssuedDuringPeriodSharesStockOptionsExercisedAndRestrictedStockAwardForfeitures_019eb20b-da8e-7505-9b7a-dcc0fb085743" xlink:href="nvcr-20260630.xsd#nvcr_StockIssuedDuringPeriodSharesStockOptionsExercisedAndRestrictedStockAwardForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:to="loc_nvcr_StockIssuedDuringPeriodSharesStockOptionsExercisedAndRestrictedStockAwardForfeitures_019eb20b-da8e-7505-9b7a-dcc0fb085743" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_StockIssuedDuringPeriodValueStockOptionsExercisedAndRestrictedStockAwardForfeitures_019eb20b-da8e-758a-a143-d61f5c88aead" xlink:href="nvcr-20260630.xsd#nvcr_StockIssuedDuringPeriodValueStockOptionsExercisedAndRestrictedStockAwardForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:to="loc_nvcr_StockIssuedDuringPeriodValueStockOptionsExercisedAndRestrictedStockAwardForfeitures_019eb20b-da8e-758a-a143-d61f5c88aead" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019eb20b-da8e-7fed-aacb-065caf69a50b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019eb20b-da8e-7fed-aacb-065caf69a50b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019eb20b-da8e-72d3-9e68-d15d3827694f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019eb20b-da8e-72d3-9e68-d15d3827694f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019eb20b-da8e-71cc-aab4-27e5941e4346" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019eb20b-da8e-765d-8c83-a359a3ae9f1f" xlink:to="loc_us-gaap_NetIncomeLoss_019eb20b-da8e-71cc-aab4-27e5941e4346" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_019eb20b-da8e-775d-a834-c22a77d79562" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019eb20b-da8e-7dd6-b3c9-44445cd30931" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/CASHCASHEQUIVALENTSANDSHORTTERMINVESTMENTSDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#CASHCASHEQUIVALENTSANDSHORTTERMINVESTMENTSDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/CASHCASHEQUIVALENTSANDSHORTTERMINVESTMENTSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019eb20b-da8e-72e6-9f6b-cc63b767131f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019eb20b-da8e-72e6-9f6b-cc63b767131f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_019eb20b-da8e-7fa5-8047-3277ba767056" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019eb20b-da8e-72e6-9f6b-cc63b767131f" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_019eb20b-da8e-7fa5-8047-3277ba767056" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7fa5-8047-3277ba767056_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_019eb20b-da8e-7fa5-8047-3277ba767056" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7fa5-8047-3277ba767056_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7ba0-90fc-a1efa90be8af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_019eb20b-da8e-7fa5-8047-3277ba767056" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7ba0-90fc-a1efa90be8af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashMember_019eb20b-da8e-7f71-8f16-852bc8e897d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7ba0-90fc-a1efa90be8af" xlink:to="loc_us-gaap_CashMember_019eb20b-da8e-7f71-8f16-852bc8e897d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_019eb20b-da8e-76f6-9e1b-dd5b53bb8a2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7ba0-90fc-a1efa90be8af" xlink:to="loc_us-gaap_MoneyMarketFundsMember_019eb20b-da8e-76f6-9e1b-dd5b53bb8a2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_019eb20b-da8e-7bf1-aa2a-9694209a41b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7ba0-90fc-a1efa90be8af" xlink:to="loc_us-gaap_CertificatesOfDepositMember_019eb20b-da8e-7bf1-aa2a-9694209a41b9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfFinancialPositionLocationBalanceAxis_019eb20b-da8e-7e09-bc50-9d44935b45a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfFinancialPositionLocationBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019eb20b-da8e-72e6-9f6b-cc63b767131f" xlink:to="loc_us-gaap_StatementOfFinancialPositionLocationBalanceAxis_019eb20b-da8e-7e09-bc50-9d44935b45a0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-da8e-7e6b-b6e2-af138a9b16d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019eb20b-da8e-72e6-9f6b-cc63b767131f" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-da8e-7e6b-b6e2-af138a9b16d2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-7e6b-b6e2-af138a9b16d2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-da8e-7e6b-b6e2-af138a9b16d2" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-7e6b-b6e2-af138a9b16d2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-70f3-93c2-7c8db154febe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-da8e-7e6b-b6e2-af138a9b16d2" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-70f3-93c2-7c8db154febe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019eb20b-da8e-7d41-b82a-9bf621b0469c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-70f3-93c2-7c8db154febe" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019eb20b-da8e-7d41-b82a-9bf621b0469c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019eb20b-da8e-7bab-bcbf-97b76bce902d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-70f3-93c2-7c8db154febe" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019eb20b-da8e-7bab-bcbf-97b76bce902d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019eb20b-da8e-767f-af53-b286502ff8ec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019eb20b-da8e-72e6-9f6b-cc63b767131f" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019eb20b-da8e-767f-af53-b286502ff8ec" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-767f-af53-b286502ff8ec_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb20b-da8e-767f-af53-b286502ff8ec" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-767f-af53-b286502ff8ec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-7a0f-92f2-535f60bb769a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb20b-da8e-767f-af53-b286502ff8ec" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-7a0f-92f2-535f60bb769a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_019eb20b-da8e-7e6d-934b-2a554ce06a72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-7a0f-92f2-535f60bb769a" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_019eb20b-da8e-7e6d-934b-2a554ce06a72" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019eb20b-da8e-7b3e-b72f-d8159c04d78e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-7a0f-92f2-535f60bb769a" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019eb20b-da8e-7b3e-b72f-d8159c04d78e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019eb20b-da8e-7fb9-92cd-60cb4db8c484" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019eb20b-da8e-7fb9-92cd-60cb4db8c484" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019eb20b-da8e-7a4e-9f79-4ccf68ec3302" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019eb20b-da8e-7a4e-9f79-4ccf68ec3302" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecurities_019eb20b-da8e-71eb-8f2f-ca0c8f310e4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HeldToMaturitySecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:to="loc_us-gaap_HeldToMaturitySecurities_019eb20b-da8e-71eb-8f2f-ca0c8f310e4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_019eb20b-da8e-716f-9fe0-899658bf4099" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_019eb20b-da8e-716f-9fe0-899658bf4099" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_019eb20b-da8e-7bfc-b465-c934b16565d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_019eb20b-da8e-7bfc-b465-c934b16565d0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019eb20b-da8e-7a9a-99db-283d09ecb973" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HeldToMaturitySecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019eb20b-da8e-7a9a-99db-283d09ecb973" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesAmortizedCost_019eb20b-da8e-75f1-8b74-43936afd02ef" xlink:href="nvcr-20260630.xsd#nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesAmortizedCost_019eb20b-da8e-75f1-8b74-43936afd02ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedGain_019eb20b-da8e-7334-a420-7aa6db47e986" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedGain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedGain_019eb20b-da8e-7334-a420-7aa6db47e986" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedLoss_019eb20b-da8e-7bde-b29b-4c0d9937351d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedLoss_019eb20b-da8e-7bde-b29b-4c0d9937351d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesFairValue_019eb20b-da8e-71c5-bedf-e17d0b974911" xlink:href="nvcr-20260630.xsd#nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesFairValue_019eb20b-da8e-71c5-bedf-e17d0b974911" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecurities_019eb20b-da8e-7e86-8932-d1b719127266" xlink:href="nvcr-20260630.xsd#nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecurities_019eb20b-da8e-7e86-8932-d1b719127266" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/CASHCASHEQUIVALENTSANDSHORTTERMINVESTMENTSDetails_1" xlink:type="simple" xlink:href="nvcr-20260630.xsd#CASHCASHEQUIVALENTSANDSHORTTERMINVESTMENTSDetails_1"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/CASHCASHEQUIVALENTSANDSHORTTERMINVESTMENTSDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019eb20b-da8e-72e6-9f6b-cc63b767131f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019eb20b-da8e-72e6-9f6b-cc63b767131f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_019eb20b-da8e-7fa5-8047-3277ba767056" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019eb20b-da8e-72e6-9f6b-cc63b767131f" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_019eb20b-da8e-7fa5-8047-3277ba767056" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7fa5-8047-3277ba767056_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_019eb20b-da8e-7fa5-8047-3277ba767056" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7fa5-8047-3277ba767056_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7ba0-90fc-a1efa90be8af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_019eb20b-da8e-7fa5-8047-3277ba767056" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7ba0-90fc-a1efa90be8af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashMember_019eb20b-da8e-7f71-8f16-852bc8e897d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7ba0-90fc-a1efa90be8af" xlink:to="loc_us-gaap_CashMember_019eb20b-da8e-7f71-8f16-852bc8e897d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_019eb20b-da8e-76f6-9e1b-dd5b53bb8a2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7ba0-90fc-a1efa90be8af" xlink:to="loc_us-gaap_MoneyMarketFundsMember_019eb20b-da8e-76f6-9e1b-dd5b53bb8a2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_019eb20b-da8e-7bf1-aa2a-9694209a41b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019eb20b-da8e-7ba0-90fc-a1efa90be8af" xlink:to="loc_us-gaap_CertificatesOfDepositMember_019eb20b-da8e-7bf1-aa2a-9694209a41b9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-da8e-7e6b-b6e2-af138a9b16d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019eb20b-da8e-72e6-9f6b-cc63b767131f" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-da8e-7e6b-b6e2-af138a9b16d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-7e6b-b6e2-af138a9b16d2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-da8e-7e6b-b6e2-af138a9b16d2" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-7e6b-b6e2-af138a9b16d2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-70f3-93c2-7c8db154febe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-da8e-7e6b-b6e2-af138a9b16d2" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-70f3-93c2-7c8db154febe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019eb20b-da8e-7d41-b82a-9bf621b0469c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-70f3-93c2-7c8db154febe" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019eb20b-da8e-7d41-b82a-9bf621b0469c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019eb20b-da8e-7bab-bcbf-97b76bce902d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-da8e-70f3-93c2-7c8db154febe" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019eb20b-da8e-7bab-bcbf-97b76bce902d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019eb20b-da8e-767f-af53-b286502ff8ec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019eb20b-da8e-72e6-9f6b-cc63b767131f" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019eb20b-da8e-767f-af53-b286502ff8ec" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-767f-af53-b286502ff8ec_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb20b-da8e-767f-af53-b286502ff8ec" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-767f-af53-b286502ff8ec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-7a0f-92f2-535f60bb769a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019eb20b-da8e-767f-af53-b286502ff8ec" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-7a0f-92f2-535f60bb769a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_019eb20b-da8e-7e6d-934b-2a554ce06a72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-7a0f-92f2-535f60bb769a" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_019eb20b-da8e-7e6d-934b-2a554ce06a72" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019eb20b-da8e-7b3e-b72f-d8159c04d78e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019eb20b-da8e-7a0f-92f2-535f60bb769a" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019eb20b-da8e-7b3e-b72f-d8159c04d78e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019eb20b-da8e-7fb9-92cd-60cb4db8c484" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019eb20b-da8e-7fb9-92cd-60cb4db8c484" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019eb20b-da8e-7a4e-9f79-4ccf68ec3302" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019eb20b-da8e-7a4e-9f79-4ccf68ec3302" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecurities_019eb20b-da8e-71eb-8f2f-ca0c8f310e4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HeldToMaturitySecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:to="loc_us-gaap_HeldToMaturitySecurities_019eb20b-da8e-71eb-8f2f-ca0c8f310e4f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_019eb20b-da8e-716f-9fe0-899658bf4099" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_019eb20b-da8e-716f-9fe0-899658bf4099" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_019eb20b-da8e-7bfc-b465-c934b16565d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_019eb20b-da8e-7bfc-b465-c934b16565d0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019eb20b-da8e-7a9a-99db-283d09ecb973" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HeldToMaturitySecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityFairValueAbstract_019eb20b-da8e-7a28-8bcc-2bba59e13010" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_019eb20b-da8e-7a9a-99db-283d09ecb973" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesAmortizedCost_019eb20b-da8e-75f1-8b74-43936afd02ef" xlink:href="nvcr-20260630.xsd#nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesAmortizedCost_019eb20b-da8e-75f1-8b74-43936afd02ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedGain_019eb20b-da8e-7334-a420-7aa6db47e986" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedGain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedGain_019eb20b-da8e-7334-a420-7aa6db47e986" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedLoss_019eb20b-da8e-7bde-b29b-4c0d9937351d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturityCumulativeUnrecognizedLoss_019eb20b-da8e-7bde-b29b-4c0d9937351d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesFairValue_019eb20b-da8e-71c5-bedf-e17d0b974911" xlink:href="nvcr-20260630.xsd#nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecuritiesFairValue_019eb20b-da8e-71c5-bedf-e17d0b974911" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecurities_019eb20b-da8e-7e86-8932-d1b719127266" xlink:href="nvcr-20260630.xsd#nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019eb20b-da8e-7b98-aea1-bdc2e3f7c900" xlink:to="loc_nvcr_CashCashEquivalentsAvailableForSaleAndHeldToMaturityDebtSecurities_019eb20b-da8e-7e86-8932-d1b719127266" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/LONGTERMDEBTNETSeniorSecuredCreditFacilityNarrativeDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#LONGTERMDEBTNETSeniorSecuredCreditFacilityNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/LONGTERMDEBTNETSeniorSecuredCreditFacilityNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019eb20b-da8e-744d-973d-dda432c129e9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_us-gaap_DebtInstrumentTable_019eb20b-da8e-744d-973d-dda432c129e9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019eb20b-da8e-7959-8602-e8e5e45ef38d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019eb20b-da8e-744d-973d-dda432c129e9" xlink:to="loc_us-gaap_CreditFacilityAxis_019eb20b-da8e-7959-8602-e8e5e45ef38d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019eb20b-da8e-7959-8602-e8e5e45ef38d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019eb20b-da8e-7959-8602-e8e5e45ef38d" xlink:to="loc_us-gaap_CreditFacilityDomain_019eb20b-da8e-7959-8602-e8e5e45ef38d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019eb20b-da8e-7799-895c-66d38071bad1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019eb20b-da8e-7959-8602-e8e5e45ef38d" xlink:to="loc_us-gaap_CreditFacilityDomain_019eb20b-da8e-7799-895c-66d38071bad1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019eb20b-da8e-7631-98dc-e5cbc83f2f2a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019eb20b-da8e-7799-895c-66d38071bad1" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019eb20b-da8e-7631-98dc-e5cbc83f2f2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019eb20b-da8e-781e-9d94-5dae47797a18" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019eb20b-da8e-744d-973d-dda432c129e9" xlink:to="loc_us-gaap_DebtInstrumentAxis_019eb20b-da8e-781e-9d94-5dae47797a18" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-da8e-781e-9d94-5dae47797a18_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019eb20b-da8e-781e-9d94-5dae47797a18" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-da8e-781e-9d94-5dae47797a18_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-da8e-759f-b146-850c652905ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019eb20b-da8e-781e-9d94-5dae47797a18" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-da8e-759f-b146-850c652905ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_A2024CreditFacilityMember_019eb20b-da8e-7d9e-94d8-487b85f971af" xlink:href="nvcr-20260630.xsd#nvcr_A2024CreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-da8e-759f-b146-850c652905ed" xlink:to="loc_nvcr_A2024CreditFacilityMember_019eb20b-da8e-7d9e-94d8-487b85f971af" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_A2024CreditFacilityTrancheAMember_019eb20b-da8e-79f9-b027-690f6a016a56" xlink:href="nvcr-20260630.xsd#nvcr_A2024CreditFacilityTrancheAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-da8e-759f-b146-850c652905ed" xlink:to="loc_nvcr_A2024CreditFacilityTrancheAMember_019eb20b-da8e-79f9-b027-690f6a016a56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_A2024CreditFacilityTrancheBMember_019eb20b-da8e-73be-902e-070710e70efd" xlink:href="nvcr-20260630.xsd#nvcr_A2024CreditFacilityTrancheBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-da8e-759f-b146-850c652905ed" xlink:to="loc_nvcr_A2024CreditFacilityTrancheBMember_019eb20b-da8e-73be-902e-070710e70efd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_A2024CreditFacilityTrancheCMember_019eb20b-da8e-79bd-a688-5c5446a61758" xlink:href="nvcr-20260630.xsd#nvcr_A2024CreditFacilityTrancheCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-da8e-759f-b146-850c652905ed" xlink:to="loc_nvcr_A2024CreditFacilityTrancheCMember_019eb20b-da8e-79bd-a688-5c5446a61758" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_A2024CreditFacilityTrancheDMember_019eb20b-da8e-729c-9830-a28f2a1a15ca" xlink:href="nvcr-20260630.xsd#nvcr_A2024CreditFacilityTrancheDMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-da8e-759f-b146-850c652905ed" xlink:to="loc_nvcr_A2024CreditFacilityTrancheDMember_019eb20b-da8e-729c-9830-a28f2a1a15ca" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019eb20b-da8e-79b4-b767-65fd51cd6b54" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019eb20b-da8e-744d-973d-dda432c129e9" xlink:to="loc_srt_RangeAxis_019eb20b-da8e-79b4-b767-65fd51cd6b54" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb20b-da8e-79b4-b767-65fd51cd6b54_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019eb20b-da8e-79b4-b767-65fd51cd6b54" xlink:to="loc_srt_RangeMember_019eb20b-da8e-79b4-b767-65fd51cd6b54_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb20b-da8e-7514-b31e-8c24688b8d67" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019eb20b-da8e-79b4-b767-65fd51cd6b54" xlink:to="loc_srt_RangeMember_019eb20b-da8e-7514-b31e-8c24688b8d67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019eb20b-da8e-7f53-8645-e29c9eb1ad49" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb20b-da8e-7514-b31e-8c24688b8d67" xlink:to="loc_srt_MinimumMember_019eb20b-da8e-7f53-8645-e29c9eb1ad49" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_019eb20b-da8e-7c20-880c-9fffcb6225a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_us-gaap_DebtInstrumentTerm_019eb20b-da8e-7c20-880c-9fffcb6225a3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019eb20b-db40-7c34-835f-32c32d8e8462" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019eb20b-db40-7c34-835f-32c32d8e8462" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_LineOfCreditFacilityNumberOfDrawings_019eb20b-db40-788d-8125-71037171d701" xlink:href="nvcr-20260630.xsd#nvcr_LineOfCreditFacilityNumberOfDrawings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_nvcr_LineOfCreditFacilityNumberOfDrawings_019eb20b-db40-788d-8125-71037171d701" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_019eb20b-db40-7365-ab02-23c7e3b0e1a5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_019eb20b-db40-7365-ab02-23c7e3b0e1a5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_LineOfCreditFacilityAccordionFeatureAdditionalBorrowingCapacityOption_019eb20b-db40-7a39-83d9-e64979245122" xlink:href="nvcr-20260630.xsd#nvcr_LineOfCreditFacilityAccordionFeatureAdditionalBorrowingCapacityOption"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_nvcr_LineOfCreditFacilityAccordionFeatureAdditionalBorrowingCapacityOption_019eb20b-db40-7a39-83d9-e64979245122" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019eb20b-db40-7b3d-918b-869a8f7c307b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019eb20b-db40-7b3d-918b-869a8f7c307b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019eb20b-db40-7955-a103-89b6e6ccfaf6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019eb20b-db40-7955-a103-89b6e6ccfaf6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateIncreaseDecrease_019eb20b-db40-7a11-b8d9-15ba2213d65f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_us-gaap_DebtInstrumentInterestRateIncreaseDecrease_019eb20b-db40-7a11-b8d9-15ba2213d65f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_LinesOfCreditFacilityNumberOfRepayments_019eb20b-db40-7747-ba4b-b971943b73a5" xlink:href="nvcr-20260630.xsd#nvcr_LinesOfCreditFacilityNumberOfRepayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_nvcr_LinesOfCreditFacilityNumberOfRepayments_019eb20b-db40-7747-ba4b-b971943b73a5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_DebtCovenantFinalPaymentOfOutstandingPrincipalDueAnniversaryOfClosingYear_019eb20b-db40-74b4-849b-e96378fe40e1" xlink:href="nvcr-20260630.xsd#nvcr_DebtCovenantFinalPaymentOfOutstandingPrincipalDueAnniversaryOfClosingYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_nvcr_DebtCovenantFinalPaymentOfOutstandingPrincipalDueAnniversaryOfClosingYear_019eb20b-db40-74b4-849b-e96378fe40e1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_019eb20b-db40-7683-92b7-445ba6d0014f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-da8e-7242-bcb3-f1c133e40dd0" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_019eb20b-db40-7683-92b7-445ba6d0014f" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/LONGTERMDEBTNETScheduleofLiabilityandEquityComponentsoftheSeniorSecuredCreditFacilityDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#LONGTERMDEBTNETScheduleofLiabilityandEquityComponentsoftheSeniorSecuredCreditFacilityDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/LONGTERMDEBTNETScheduleofLiabilityandEquityComponentsoftheSeniorSecuredCreditFacilityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019eb20b-db40-79bc-816b-f322458fcc84" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019eb20b-db40-72c7-9b27-2fce0bde97b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-db40-79bc-816b-f322458fcc84" xlink:to="loc_us-gaap_DebtInstrumentTable_019eb20b-db40-72c7-9b27-2fce0bde97b8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019eb20b-db40-7f05-914a-3fd647269621" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019eb20b-db40-72c7-9b27-2fce0bde97b8" xlink:to="loc_us-gaap_CreditFacilityAxis_019eb20b-db40-7f05-914a-3fd647269621" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019eb20b-db40-7f05-914a-3fd647269621_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019eb20b-db40-7f05-914a-3fd647269621" xlink:to="loc_us-gaap_CreditFacilityDomain_019eb20b-db40-7f05-914a-3fd647269621_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019eb20b-db40-7916-9191-0802c3105357" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019eb20b-db40-7f05-914a-3fd647269621" xlink:to="loc_us-gaap_CreditFacilityDomain_019eb20b-db40-7916-9191-0802c3105357" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019eb20b-db40-7e49-a2e9-075a6077da09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019eb20b-db40-7916-9191-0802c3105357" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019eb20b-db40-7e49-a2e9-075a6077da09" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019eb20b-db40-7b27-8139-7a70ed5de453" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019eb20b-db40-72c7-9b27-2fce0bde97b8" xlink:to="loc_us-gaap_DebtInstrumentAxis_019eb20b-db40-7b27-8139-7a70ed5de453" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-db40-7b27-8139-7a70ed5de453_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019eb20b-db40-7b27-8139-7a70ed5de453" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-db40-7b27-8139-7a70ed5de453_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-db40-75fa-94fc-fe5fe6e40df3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019eb20b-db40-7b27-8139-7a70ed5de453" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-db40-75fa-94fc-fe5fe6e40df3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_A2024CreditFacilityTrancheAMember_019eb20b-db40-72da-81b8-1fdaf7241d21" xlink:href="nvcr-20260630.xsd#nvcr_A2024CreditFacilityTrancheAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-db40-75fa-94fc-fe5fe6e40df3" xlink:to="loc_nvcr_A2024CreditFacilityTrancheAMember_019eb20b-db40-72da-81b8-1fdaf7241d21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-db40-72ce-ba8d-96be5c811b51" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019eb20b-db40-72c7-9b27-2fce0bde97b8" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-db40-72ce-ba8d-96be5c811b51" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-db40-72ce-ba8d-96be5c811b51_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-db40-72ce-ba8d-96be5c811b51" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-db40-72ce-ba8d-96be5c811b51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-db40-7c25-84e0-d3f0fe7354f8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019eb20b-db40-72ce-ba8d-96be5c811b51" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-db40-7c25-84e0-d3f0fe7354f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019eb20b-db40-754d-aea8-bcf7f90d953a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019eb20b-db40-7c25-84e0-d3f0fe7354f8" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019eb20b-db40-754d-aea8-bcf7f90d953a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019eb20b-db40-7c9d-9648-8b7e96335b60" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-db40-79bc-816b-f322458fcc84" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019eb20b-db40-7c9d-9648-8b7e96335b60" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019eb20b-db40-78c9-bfaf-2d5932732eb8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-db40-79bc-816b-f322458fcc84" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019eb20b-db40-78c9-bfaf-2d5932732eb8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019eb20b-db40-7852-886f-10bd984190ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-db40-79bc-816b-f322458fcc84" xlink:to="loc_us-gaap_LongTermDebt_019eb20b-db40-7852-886f-10bd984190ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_019eb20b-db40-76bf-a406-3eadc548ea86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-db40-79bc-816b-f322458fcc84" xlink:to="loc_us-gaap_LongTermDebtFairValue_019eb20b-db40-76bf-a406-3eadc548ea86" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/LONGTERMDEBTNETAmortizationofFinanceExpenseSeniorSecuredCreditFacilityDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#LONGTERMDEBTNETAmortizationofFinanceExpenseSeniorSecuredCreditFacilityDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/LONGTERMDEBTNETAmortizationofFinanceExpenseSeniorSecuredCreditFacilityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019eb20b-db40-7b75-a484-01593b2989b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019eb20b-db40-7722-8245-6cad3d9b4e03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-db40-7b75-a484-01593b2989b0" xlink:to="loc_us-gaap_DebtInstrumentTable_019eb20b-db40-7722-8245-6cad3d9b4e03" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019eb20b-db40-7f71-97f9-81346424a1d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019eb20b-db40-7722-8245-6cad3d9b4e03" xlink:to="loc_us-gaap_CreditFacilityAxis_019eb20b-db40-7f71-97f9-81346424a1d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019eb20b-db40-7f71-97f9-81346424a1d2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019eb20b-db40-7f71-97f9-81346424a1d2" xlink:to="loc_us-gaap_CreditFacilityDomain_019eb20b-db40-7f71-97f9-81346424a1d2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019eb20b-db40-7748-8d4a-d1a296ded50d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019eb20b-db40-7f71-97f9-81346424a1d2" xlink:to="loc_us-gaap_CreditFacilityDomain_019eb20b-db40-7748-8d4a-d1a296ded50d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019eb20b-db40-73c9-a140-8ca300f92a9d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019eb20b-db40-7748-8d4a-d1a296ded50d" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019eb20b-db40-73c9-a140-8ca300f92a9d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019eb20b-db40-7931-a46a-a6c3e64da147" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019eb20b-db40-7722-8245-6cad3d9b4e03" xlink:to="loc_us-gaap_DebtInstrumentAxis_019eb20b-db40-7931-a46a-a6c3e64da147" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-db40-7931-a46a-a6c3e64da147_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019eb20b-db40-7931-a46a-a6c3e64da147" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-db40-7931-a46a-a6c3e64da147_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-db40-7064-a07a-a8f4b28acef7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019eb20b-db40-7931-a46a-a6c3e64da147" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-db40-7064-a07a-a8f4b28acef7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_A2024CreditFacilityTrancheAMember_019eb20b-db40-79c6-9fec-eee5308d3f4e" xlink:href="nvcr-20260630.xsd#nvcr_A2024CreditFacilityTrancheAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019eb20b-db40-7064-a07a-a8f4b28acef7" xlink:to="loc_nvcr_A2024CreditFacilityTrancheAMember_019eb20b-db40-79c6-9fec-eee5308d3f4e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseLongTermDebt_019eb20b-db40-7b45-aacd-ed89172251d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-db40-7b75-a484-01593b2989b0" xlink:to="loc_us-gaap_InterestExpenseLongTermDebt_019eb20b-db40-7b45-aacd-ed89172251d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_019eb20b-db40-7a3b-9b1f-6aef7f773c4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-db40-7b75-a484-01593b2989b0" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_019eb20b-db40-7a3b-9b1f-6aef7f773c4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_019eb20b-db40-7ac9-b57c-66237d7d4ece" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019eb20b-db40-7b75-a484-01593b2989b0" xlink:to="loc_us-gaap_InterestExpenseDebt_019eb20b-db40-7ac9-b57c-66237d7d4ece" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/REVENUERECOGNITIONScheduleofRevenuesbyGeographicRegionDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#REVENUERECOGNITIONScheduleofRevenuesbyGeographicRegionDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/REVENUERECOGNITIONScheduleofRevenuesbyGeographicRegionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019eb20b-db40-7264-8ab6-2aa96bae0d05" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019eb20b-db40-7ecd-96ae-54f96cc70731" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019eb20b-db40-7264-8ab6-2aa96bae0d05" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019eb20b-db40-7ecd-96ae-54f96cc70731" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019eb20b-db40-7ba1-8484-f371dd052c59" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019eb20b-db40-7ecd-96ae-54f96cc70731" xlink:to="loc_srt_StatementGeographicalAxis_019eb20b-db40-7ba1-8484-f371dd052c59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb20b-db40-7ba1-8484-f371dd052c59_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019eb20b-db40-7ba1-8484-f371dd052c59" xlink:to="loc_srt_SegmentGeographicalDomain_019eb20b-db40-7ba1-8484-f371dd052c59_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb20b-db40-7d71-87d9-eab5524362b2" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019eb20b-db40-7ba1-8484-f371dd052c59" xlink:to="loc_srt_SegmentGeographicalDomain_019eb20b-db40-7d71-87d9-eab5524362b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb20b-db40-7ce8-b42f-87cb7fbbe718" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb20b-db40-7d71-87d9-eab5524362b2" xlink:to="loc_country_US_019eb20b-db40-7ce8-b42f-87cb7fbbe718" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_DE_019eb20b-db40-7aef-b78a-1f7e30037215" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_DE"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb20b-db40-7d71-87d9-eab5524362b2" xlink:to="loc_country_DE_019eb20b-db40-7aef-b78a-1f7e30037215" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_FR_019eb20b-db40-70ca-b691-6525c476a85c" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_FR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb20b-db40-7d71-87d9-eab5524362b2" xlink:to="loc_country_FR_019eb20b-db40-70ca-b691-6525c476a85c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_JP_019eb20b-db40-7c22-aa1c-63f15148dfa2" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_JP"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb20b-db40-7d71-87d9-eab5524362b2" xlink:to="loc_country_JP_019eb20b-db40-7c22-aa1c-63f15148dfa2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_OtherInternationalMarketsMember_019eb20b-db40-73a4-8925-b23c016f73ee" xlink:href="nvcr-20260630.xsd#nvcr_OtherInternationalMarketsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb20b-db40-7d71-87d9-eab5524362b2" xlink:to="loc_nvcr_OtherInternationalMarketsMember_019eb20b-db40-73a4-8925-b23c016f73ee" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_InternationalMarketsMember_019eb20b-db40-7544-8c36-5c180c71657f" xlink:href="nvcr-20260630.xsd#nvcr_InternationalMarketsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb20b-db40-7d71-87d9-eab5524362b2" xlink:to="loc_nvcr_InternationalMarketsMember_019eb20b-db40-7544-8c36-5c180c71657f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CN_019eb20b-db40-7099-b904-f0bf9a9b9701" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_CN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb20b-db40-7d71-87d9-eab5524362b2" xlink:to="loc_country_CN_019eb20b-db40-7099-b904-f0bf9a9b9701" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019eb20b-db40-7c81-9ad9-84b695dda96a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019eb20b-db40-7264-8ab6-2aa96bae0d05" xlink:to="loc_us-gaap_Revenues_019eb20b-db40-7c81-9ad9-84b695dda96a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/REVENUERECOGNITIONRevenueRecognizedAccordingPerformancePeriodDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#REVENUERECOGNITIONRevenueRecognizedAccordingPerformancePeriodDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/REVENUERECOGNITIONRevenueRecognizedAccordingPerformancePeriodDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019eb20b-db40-7695-afcf-99b5202a9359" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019eb20b-db40-74fb-b745-ad42fda7735d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019eb20b-db40-7695-afcf-99b5202a9359" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019eb20b-db40-74fb-b745-ad42fda7735d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInAxis_019eb20b-db40-7dd7-b034-a6ccdbdee8ca" xlink:href="nvcr-20260630.xsd#nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019eb20b-db40-74fb-b745-ad42fda7735d" xlink:to="loc_nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInAxis_019eb20b-db40-7dd7-b034-a6ccdbdee8ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInDomain_019eb20b-db40-7dd7-b034-a6ccdbdee8ca_default" xlink:href="nvcr-20260630.xsd#nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInAxis_019eb20b-db40-7dd7-b034-a6ccdbdee8ca" xlink:to="loc_nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInDomain_019eb20b-db40-7dd7-b034-a6ccdbdee8ca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInDomain_019eb20b-db40-77a8-a88b-803670fc3f68" xlink:href="nvcr-20260630.xsd#nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInAxis_019eb20b-db40-7dd7-b034-a6ccdbdee8ca" xlink:to="loc_nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInDomain_019eb20b-db40-77a8-a88b-803670fc3f68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_ReportingPeriodMember_019eb20b-db40-7319-a24e-967afd0d49d8" xlink:href="nvcr-20260630.xsd#nvcr_ReportingPeriodMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInDomain_019eb20b-db40-77a8-a88b-803670fc3f68" xlink:to="loc_nvcr_ReportingPeriodMember_019eb20b-db40-7319-a24e-967afd0d49d8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_PreviousPeriodsMember_019eb20b-db40-7533-847c-928be6643e43" xlink:href="nvcr-20260630.xsd#nvcr_PreviousPeriodsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_RevenuePerformanceObligationPeriodObligationWasSatisfiedInDomain_019eb20b-db40-77a8-a88b-803670fc3f68" xlink:to="loc_nvcr_PreviousPeriodsMember_019eb20b-db40-7533-847c-928be6643e43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019eb20b-db40-7e42-8245-fbc730425000" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019eb20b-db40-7695-afcf-99b5202a9359" xlink:to="loc_us-gaap_Revenues_019eb20b-db40-7e42-8245-fbc730425000" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/SHAREOPTIONPLANSANDESPPNarrativeDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#SHAREOPTIONPLANSANDESPPNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/SHAREOPTIONPLANSANDESPPNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_ShareCapitalLineItems_019eb20b-db40-79cb-853a-14be74cb9fe0" xlink:href="nvcr-20260630.xsd#nvcr_ShareCapitalLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_ScheduleOfShareCapitalTable_019eb20b-db40-760d-b082-3269cb95a209" xlink:href="nvcr-20260630.xsd#nvcr_ScheduleOfShareCapitalTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_nvcr_ShareCapitalLineItems_019eb20b-db40-79cb-853a-14be74cb9fe0" xlink:to="loc_nvcr_ScheduleOfShareCapitalTable_019eb20b-db40-760d-b082-3269cb95a209" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_019eb20b-db40-7aa7-a7b5-e00b2288149e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nvcr_ScheduleOfShareCapitalTable_019eb20b-db40-760d-b082-3269cb95a209" xlink:to="loc_us-gaap_PlanNameAxis_019eb20b-db40-7aa7-a7b5-e00b2288149e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019eb20b-db40-7aa7-a7b5-e00b2288149e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_019eb20b-db40-7aa7-a7b5-e00b2288149e" xlink:to="loc_us-gaap_PlanNameDomain_019eb20b-db40-7aa7-a7b5-e00b2288149e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019eb20b-db40-7b13-ab3e-d372c5de0ab6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_019eb20b-db40-7aa7-a7b5-e00b2288149e" xlink:to="loc_us-gaap_PlanNameDomain_019eb20b-db40-7b13-ab3e-d372c5de0ab6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_A2024OmnibusIncentivePlanMember_019eb20b-db40-7878-a1fa-dbef50370460" xlink:href="nvcr-20260630.xsd#nvcr_A2024OmnibusIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_019eb20b-db40-7b13-ab3e-d372c5de0ab6" xlink:to="loc_nvcr_A2024OmnibusIncentivePlanMember_019eb20b-db40-7878-a1fa-dbef50370460" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_TwoThousandFifteenPlanMember_019eb20b-db40-733e-a3ef-28133f3e32dc" xlink:href="nvcr-20260630.xsd#nvcr_TwoThousandFifteenPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_019eb20b-db40-7b13-ab3e-d372c5de0ab6" xlink:to="loc_nvcr_TwoThousandFifteenPlanMember_019eb20b-db40-733e-a3ef-28133f3e32dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_A2025EmployeeSharePurchasePlanESPPMember_019eb20b-db40-7cfc-a410-96f9971c21ba" xlink:href="nvcr-20260630.xsd#nvcr_A2025EmployeeSharePurchasePlanESPPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_019eb20b-db40-7b13-ab3e-d372c5de0ab6" xlink:to="loc_nvcr_A2025EmployeeSharePurchasePlanESPPMember_019eb20b-db40-7cfc-a410-96f9971c21ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019eb20b-db40-7915-9815-6bb2ca45b96c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nvcr_ScheduleOfShareCapitalTable_019eb20b-db40-760d-b082-3269cb95a209" xlink:to="loc_us-gaap_AwardTypeAxis_019eb20b-db40-7915-9815-6bb2ca45b96c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7915-9815-6bb2ca45b96c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019eb20b-db40-7915-9815-6bb2ca45b96c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7915-9815-6bb2ca45b96c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-759e-8a9b-d98b6a5e0054" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019eb20b-db40-7915-9815-6bb2ca45b96c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-759e-8a9b-d98b6a5e0054" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_019eb20b-db40-733b-bf57-fa9768433a86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-759e-8a9b-d98b6a5e0054" xlink:to="loc_us-gaap_EmployeeStockOptionMember_019eb20b-db40-733b-bf57-fa9768433a86" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019eb20b-db40-742b-a44e-6b1bb55b7cd6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-759e-8a9b-d98b6a5e0054" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019eb20b-db40-742b-a44e-6b1bb55b7cd6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_PerformanceBasedShareUnitsPSUsMember_019eb20b-db40-7ff7-a3ee-99e060c37a02" xlink:href="nvcr-20260630.xsd#nvcr_PerformanceBasedShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-759e-8a9b-d98b6a5e0054" xlink:to="loc_nvcr_PerformanceBasedShareUnitsPSUsMember_019eb20b-db40-7ff7-a3ee-99e060c37a02" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019eb20b-db40-7734-8f42-a7186b32b5e6" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nvcr_ScheduleOfShareCapitalTable_019eb20b-db40-760d-b082-3269cb95a209" xlink:to="loc_srt_RangeAxis_019eb20b-db40-7734-8f42-a7186b32b5e6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb20b-db40-7734-8f42-a7186b32b5e6_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019eb20b-db40-7734-8f42-a7186b32b5e6" xlink:to="loc_srt_RangeMember_019eb20b-db40-7734-8f42-a7186b32b5e6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb20b-db40-7486-bb94-3c2d916a8b14" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019eb20b-db40-7734-8f42-a7186b32b5e6" xlink:to="loc_srt_RangeMember_019eb20b-db40-7486-bb94-3c2d916a8b14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019eb20b-db40-7b80-9a11-1a0a65cd0da7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb20b-db40-7486-bb94-3c2d916a8b14" xlink:to="loc_srt_MinimumMember_019eb20b-db40-7b80-9a11-1a0a65cd0da7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019eb20b-db40-7298-8b66-2ef94594ef2f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb20b-db40-7486-bb94-3c2d916a8b14" xlink:to="loc_srt_MaximumMember_019eb20b-db40-7298-8b66-2ef94594ef2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusAxis_019f36c3-cc26-7f6a-9e99-4eeb00841d8d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nvcr_ScheduleOfShareCapitalTable_019eb20b-db40-760d-b082-3269cb95a209" xlink:to="loc_us-gaap_GranteeStatusAxis_019f36c3-cc26-7f6a-9e99-4eeb00841d8d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_019f36c3-cc26-7f6a-9e99-4eeb00841d8d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GranteeStatusAxis_019f36c3-cc26-7f6a-9e99-4eeb00841d8d" xlink:to="loc_us-gaap_GranteeStatusDomain_019f36c3-cc26-7f6a-9e99-4eeb00841d8d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_019f36c3-cc26-7d93-8ad8-cb054d659174" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GranteeStatusAxis_019f36c3-cc26-7f6a-9e99-4eeb00841d8d" xlink:to="loc_us-gaap_GranteeStatusDomain_019f36c3-cc26-7d93-8ad8-cb054d659174" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedPaymentArrangementNonemployeeMember_019f36c4-03bb-799e-bf58-73beec65be79" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedPaymentArrangementNonemployeeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GranteeStatusDomain_019f36c3-cc26-7d93-8ad8-cb054d659174" xlink:to="loc_us-gaap_ShareBasedPaymentArrangementNonemployeeMember_019f36c4-03bb-799e-bf58-73beec65be79" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_019ee085-50cf-7b51-86d7-9a918239b402" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_ShareCapitalLineItems_019eb20b-db40-79cb-853a-14be74cb9fe0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_019ee085-50cf-7b51-86d7-9a918239b402" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_019eb20b-db40-72ea-8b18-2c1412e64b53" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_ShareCapitalLineItems_019eb20b-db40-79cb-853a-14be74cb9fe0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_019eb20b-db40-72ea-8b18-2c1412e64b53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019eb20b-db40-7586-8d14-99bc0c26442b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_ShareCapitalLineItems_019eb20b-db40-79cb-853a-14be74cb9fe0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019eb20b-db40-7586-8d14-99bc0c26442b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_019eb20b-db40-7a3a-897c-c63e8e5f5677" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_ShareCapitalLineItems_019eb20b-db40-79cb-853a-14be74cb9fe0" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_019eb20b-db40-7a3a-897c-c63e8e5f5677" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPercentageOfAvailableSharePoolExemptFromVestingPeriodRequirements_019ed123-d408-77d3-ba54-9f385e921f0f" xlink:href="nvcr-20260630.xsd#nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPercentageOfAvailableSharePoolExemptFromVestingPeriodRequirements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_ShareCapitalLineItems_019eb20b-db40-79cb-853a-14be74cb9fe0" xlink:to="loc_nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPercentageOfAvailableSharePoolExemptFromVestingPeriodRequirements_019ed123-d408-77d3-ba54-9f385e921f0f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_019eb20b-db40-70e2-a24b-98331be7804a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_ShareCapitalLineItems_019eb20b-db40-79cb-853a-14be74cb9fe0" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_019eb20b-db40-70e2-a24b-98331be7804a" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/SHAREOPTIONPLANSANDESPPScheduleofRSUsandPSUsDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#SHAREOPTIONPLANSANDESPPScheduleofRSUsandPSUsDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/SHAREOPTIONPLANSANDESPPScheduleofRSUsandPSUsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db40-7fe0-ae4e-b925f10263a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db40-741d-8b5b-c81843d8f812" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db40-7fe0-ae4e-b925f10263a9" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db40-741d-8b5b-c81843d8f812" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019eb20b-db40-704e-85d9-44553a634437" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db40-741d-8b5b-c81843d8f812" xlink:to="loc_us-gaap_AwardTypeAxis_019eb20b-db40-704e-85d9-44553a634437" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-704e-85d9-44553a634437_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019eb20b-db40-704e-85d9-44553a634437" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-704e-85d9-44553a634437_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7d57-88f1-a4061f402649" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019eb20b-db40-704e-85d9-44553a634437" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7d57-88f1-a4061f402649" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_RestrictedStockUnitsRSUsAndPerformanceBasedShareUnitsPSUsMember_019eb20b-db40-7f99-b0e9-5b15a5b37f08" xlink:href="nvcr-20260630.xsd#nvcr_RestrictedStockUnitsRSUsAndPerformanceBasedShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7d57-88f1-a4061f402649" xlink:to="loc_nvcr_RestrictedStockUnitsRSUsAndPerformanceBasedShareUnitsPSUsMember_019eb20b-db40-7f99-b0e9-5b15a5b37f08" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_PerformanceBasedShareUnitsPSUsMember_019eb20b-db40-738f-aa7a-ecf09e6fd869" xlink:href="nvcr-20260630.xsd#nvcr_PerformanceBasedShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7d57-88f1-a4061f402649" xlink:to="loc_nvcr_PerformanceBasedShareUnitsPSUsMember_019eb20b-db40-738f-aa7a-ecf09e6fd869" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_GrantedAxis_019eb20b-db40-7b3a-b8d6-c00eaea9bd41" xlink:href="nvcr-20260630.xsd#nvcr_GrantedAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db40-741d-8b5b-c81843d8f812" xlink:to="loc_nvcr_GrantedAxis_019eb20b-db40-7b3a-b8d6-c00eaea9bd41" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_GrantedDomain_019eb20b-db40-7b3a-b8d6-c00eaea9bd41_default" xlink:href="nvcr-20260630.xsd#nvcr_GrantedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_nvcr_GrantedAxis_019eb20b-db40-7b3a-b8d6-c00eaea9bd41" xlink:to="loc_nvcr_GrantedDomain_019eb20b-db40-7b3a-b8d6-c00eaea9bd41_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_GrantedDomain_019eb20b-db40-7dfe-8ae9-0811e83f28c3" xlink:href="nvcr-20260630.xsd#nvcr_GrantedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_nvcr_GrantedAxis_019eb20b-db40-7b3a-b8d6-c00eaea9bd41" xlink:to="loc_nvcr_GrantedDomain_019eb20b-db40-7dfe-8ae9-0811e83f28c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_AwardOneMember_019eb20b-db40-7e33-bb56-274b5f1edad0" xlink:href="nvcr-20260630.xsd#nvcr_AwardOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_GrantedDomain_019eb20b-db40-7dfe-8ae9-0811e83f28c3" xlink:to="loc_nvcr_AwardOneMember_019eb20b-db40-7e33-bb56-274b5f1edad0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_AwardTwoMember_019eb20b-db40-7f7f-a541-7107f9249460" xlink:href="nvcr-20260630.xsd#nvcr_AwardTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_GrantedDomain_019eb20b-db40-7dfe-8ae9-0811e83f28c3" xlink:to="loc_nvcr_AwardTwoMember_019eb20b-db40-7f7f-a541-7107f9249460" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_AwardThreeMember_019eb20b-db40-7ac1-a4f1-8fc484eaebf2" xlink:href="nvcr-20260630.xsd#nvcr_AwardThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_GrantedDomain_019eb20b-db40-7dfe-8ae9-0811e83f28c3" xlink:to="loc_nvcr_AwardThreeMember_019eb20b-db40-7ac1-a4f1-8fc484eaebf2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_AwardFourMember_019eb20b-db40-75c0-adb8-2a31fdf364fa" xlink:href="nvcr-20260630.xsd#nvcr_AwardFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nvcr_GrantedDomain_019eb20b-db40-7dfe-8ae9-0811e83f28c3" xlink:to="loc_nvcr_AwardFourMember_019eb20b-db40-75c0-adb8-2a31fdf364fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019eb20b-db40-7fc2-8dad-9f1dc77ef8ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db40-7fe0-ae4e-b925f10263a9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019eb20b-db40-7fc2-8dad-9f1dc77ef8ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019eb20b-db40-717b-b755-829f3ecd13a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019eb20b-db40-7fc2-8dad-9f1dc77ef8ef" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019eb20b-db40-717b-b755-829f3ecd13a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019eb20b-db40-7de1-945f-e4d595fd0380" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019eb20b-db40-7fc2-8dad-9f1dc77ef8ef" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019eb20b-db40-7de1-945f-e4d595fd0380" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019eb20b-db40-75c0-9538-c33fbe3f9416" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019eb20b-db40-7fc2-8dad-9f1dc77ef8ef" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019eb20b-db40-75c0-9538-c33fbe3f9416" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019eb20b-db40-7384-8e1b-46009cfa19bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019eb20b-db40-7fc2-8dad-9f1dc77ef8ef" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019eb20b-db40-7384-8e1b-46009cfa19bd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019eb20b-db40-78c9-b4e4-1c6bcb942e92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_019eb20b-db40-7fc2-8dad-9f1dc77ef8ef" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_019eb20b-db40-78c9-b4e4-1c6bcb942e92" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019eb20b-db40-706e-8083-a3c52a0a6dda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019eb20b-db40-77f0-8aad-2120c23dbb13" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db40-7fe0-ae4e-b925f10263a9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019eb20b-db40-77f0-8aad-2120c23dbb13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019eb20b-db40-77fc-b4e8-ee852fa87320" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019eb20b-db40-77f0-8aad-2120c23dbb13" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019eb20b-db40-77fc-b4e8-ee852fa87320" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019eb20b-db40-74c0-b49e-e5474ac06a7c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019eb20b-db40-77f0-8aad-2120c23dbb13" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019eb20b-db40-74c0-b49e-e5474ac06a7c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019eb20b-db40-72ca-8eab-2a8dd7f3c817" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019eb20b-db40-77f0-8aad-2120c23dbb13" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019eb20b-db40-72ca-8eab-2a8dd7f3c817" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWithheldForWithholdingTaxObligationWeightedAverageGrantDateFairValue_019eb20b-db40-7b5e-9423-7fb4310076e9" xlink:href="nvcr-20260630.xsd#nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWithheldForWithholdingTaxObligationWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019eb20b-db40-77f0-8aad-2120c23dbb13" xlink:to="loc_nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWithheldForWithholdingTaxObligationWeightedAverageGrantDateFairValue_019eb20b-db40-7b5e-9423-7fb4310076e9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019eb20b-db40-7201-8f22-74bf6c0130b5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_019eb20b-db40-77f0-8aad-2120c23dbb13" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019eb20b-db40-7201-8f22-74bf6c0130b5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019eb20b-db40-7af9-8e67-accaca6de5eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNotExpectedToVestNonvestedNumber_019eb20b-db40-7ca4-8c24-4ac5090bf9a2" xlink:href="nvcr-20260630.xsd#nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNotExpectedToVestNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db40-7fe0-ae4e-b925f10263a9" xlink:to="loc_nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNotExpectedToVestNonvestedNumber_019eb20b-db40-7ca4-8c24-4ac5090bf9a2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNotExpectedToVestNonvestedWeightedAverageGrantDateFairValue_019eb20b-db40-7282-b86a-8919b915a26f" xlink:href="nvcr-20260630.xsd#nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNotExpectedToVestNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db40-7fe0-ae4e-b925f10263a9" xlink:to="loc_nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNotExpectedToVestNonvestedWeightedAverageGrantDateFairValue_019eb20b-db40-7282-b86a-8919b915a26f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedAndNotExpectedToVestFairValue_019eb20b-db40-7840-ad05-6929b235294f" xlink:href="nvcr-20260630.xsd#nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedAndNotExpectedToVestFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db40-7fe0-ae4e-b925f10263a9" xlink:to="loc_nvcr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedAndNotExpectedToVestFairValue_019eb20b-db40-7840-ad05-6929b235294f" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/SHAREOPTIONPLANSANDESPPScheduleofFairValueAssumptionsUsedOnlyforEquityBasedAwardsEstimatedUsingBlackScholesOptionPricingModelDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#SHAREOPTIONPLANSANDESPPScheduleofFairValueAssumptionsUsedOnlyforEquityBasedAwardsEstimatedUsingBlackScholesOptionPricingModelDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/SHAREOPTIONPLANSANDESPPScheduleofFairValueAssumptionsUsedOnlyforEquityBasedAwardsEstimatedUsingBlackScholesOptionPricingModelDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-7fa2-aa48-f6c08cc42cf0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db40-76d5-a816-e47166a325d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-7fa2-aa48-f6c08cc42cf0" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db40-76d5-a816-e47166a325d0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019eb20b-db40-7381-b2fc-b99d2d275696" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db40-76d5-a816-e47166a325d0" xlink:to="loc_us-gaap_AwardTypeAxis_019eb20b-db40-7381-b2fc-b99d2d275696" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7381-b2fc-b99d2d275696_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019eb20b-db40-7381-b2fc-b99d2d275696" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7381-b2fc-b99d2d275696_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7e33-805b-b24fde3bb1c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019eb20b-db40-7381-b2fc-b99d2d275696" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7e33-805b-b24fde3bb1c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_019eb20b-db40-7358-a584-4d1b17562532" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7e33-805b-b24fde3bb1c9" xlink:to="loc_us-gaap_EmployeeStockOptionMember_019eb20b-db40-7358-a584-4d1b17562532" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_019eb20b-db40-7ee9-a644-c09523ee123e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db40-7e33-805b-b24fde3bb1c9" xlink:to="loc_us-gaap_EmployeeStockMember_019eb20b-db40-7ee9-a644-c09523ee123e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019eb20b-db41-789a-86c2-0b6f8a4bef20" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db40-76d5-a816-e47166a325d0" xlink:to="loc_srt_RangeAxis_019eb20b-db41-789a-86c2-0b6f8a4bef20" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb20b-db41-789a-86c2-0b6f8a4bef20_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019eb20b-db41-789a-86c2-0b6f8a4bef20" xlink:to="loc_srt_RangeMember_019eb20b-db41-789a-86c2-0b6f8a4bef20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019eb20b-db41-78a3-a3f0-6f048dca76e0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019eb20b-db41-789a-86c2-0b6f8a4bef20" xlink:to="loc_srt_RangeMember_019eb20b-db41-78a3-a3f0-6f048dca76e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019eb20b-db41-7f96-8483-8a59d72c78fc" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb20b-db41-78a3-a3f0-6f048dca76e0" xlink:to="loc_srt_MinimumMember_019eb20b-db41-7f96-8483-8a59d72c78fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019eb20b-db41-7980-a9c0-cb572d1d4213" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019eb20b-db41-78a3-a3f0-6f048dca76e0" xlink:to="loc_srt_MaximumMember_019eb20b-db41-7980-a9c0-cb572d1d4213" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_019eb20b-db41-78ca-ac05-7a802f368fed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-7fa2-aa48-f6c08cc42cf0" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_019eb20b-db41-78ca-ac05-7a802f368fed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_019eb20b-db41-704f-8ad3-e80d8857754d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-7fa2-aa48-f6c08cc42cf0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_019eb20b-db41-704f-8ad3-e80d8857754d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_019eb20b-db41-75af-b557-4eb9856e8cbe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-7fa2-aa48-f6c08cc42cf0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_019eb20b-db41-75af-b557-4eb9856e8cbe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_019eb20b-db41-767b-8fd7-3d6612d3f424" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-7fa2-aa48-f6c08cc42cf0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_019eb20b-db41-767b-8fd7-3d6612d3f424" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_019eb20b-db41-7721-b4c8-52c2fa85f102" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-7fa2-aa48-f6c08cc42cf0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_019eb20b-db41-7721-b4c8-52c2fa85f102" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_019eb20b-db41-756f-9206-b3ecac11f341" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-7fa2-aa48-f6c08cc42cf0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_019eb20b-db41-756f-9206-b3ecac11f341" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_019eb20b-db41-79d4-9f97-11ac1816f1a5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-7fa2-aa48-f6c08cc42cf0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_019eb20b-db41-79d4-9f97-11ac1816f1a5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_019eb20b-db41-7f4e-9b83-9992df43eb8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-7fa2-aa48-f6c08cc42cf0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_019eb20b-db41-7f4e-9b83-9992df43eb8b" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/SHAREOPTIONPLANSANDESPPScheduleofNoncashShareBasedCompensationExpensesRelatedtoCompanysEquityBasedAwardsDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#SHAREOPTIONPLANSANDESPPScheduleofNoncashShareBasedCompensationExpensesRelatedtoCompanysEquityBasedAwardsDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/SHAREOPTIONPLANSANDESPPScheduleofNoncashShareBasedCompensationExpensesRelatedtoCompanysEquityBasedAwardsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-782a-b9ec-7bc086752b28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db41-7cf3-9c11-17867212bd55" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-782a-b9ec-7bc086752b28" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db41-7cf3-9c11-17867212bd55" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019eb20b-db41-7669-a42a-3b2ffa352b29" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfIncomeLocationBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db41-7cf3-9c11-17867212bd55" xlink:to="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019eb20b-db41-7669-a42a-3b2ffa352b29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019eb20b-db41-7745-b0ad-5affc821545d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db41-7cf3-9c11-17867212bd55" xlink:to="loc_us-gaap_AwardTypeAxis_019eb20b-db41-7745-b0ad-5affc821545d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db41-7745-b0ad-5affc821545d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019eb20b-db41-7745-b0ad-5affc821545d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db41-7745-b0ad-5affc821545d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db41-708b-b681-b9061e2f44d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019eb20b-db41-7745-b0ad-5affc821545d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db41-708b-b681-b9061e2f44d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_PerformanceBasedShareUnitsPSUsMember_019eb20b-db41-7049-8695-4a91dfcd8ec2" xlink:href="nvcr-20260630.xsd#nvcr_PerformanceBasedShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db41-708b-b681-b9061e2f44d7" xlink:to="loc_nvcr_PerformanceBasedShareUnitsPSUsMember_019eb20b-db41-7049-8695-4a91dfcd8ec2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019eb20b-db41-7987-8ec2-afd2d6f658a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-782a-b9ec-7bc086752b28" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019eb20b-db41-7987-8ec2-afd2d6f658a0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019eb20b-db41-7975-aec3-12dadf9357ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-782a-b9ec-7bc086752b28" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019eb20b-db41-7975-aec3-12dadf9357ab" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/SHAREOPTIONPLANSANDESPPScheduleofNoncashShareBasedCompensationExpensesRelatedtoCompanysEquityBasedAwardsDetails_1" xlink:type="simple" xlink:href="nvcr-20260630.xsd#SHAREOPTIONPLANSANDESPPScheduleofNoncashShareBasedCompensationExpensesRelatedtoCompanysEquityBasedAwardsDetails_1"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/SHAREOPTIONPLANSANDESPPScheduleofNoncashShareBasedCompensationExpensesRelatedtoCompanysEquityBasedAwardsDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-782a-b9ec-7bc086752b28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db41-7cf3-9c11-17867212bd55" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-782a-b9ec-7bc086752b28" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db41-7cf3-9c11-17867212bd55" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019eb20b-db41-7745-b0ad-5affc821545d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019eb20b-db41-7cf3-9c11-17867212bd55" xlink:to="loc_us-gaap_AwardTypeAxis_019eb20b-db41-7745-b0ad-5affc821545d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db41-7745-b0ad-5affc821545d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019eb20b-db41-7745-b0ad-5affc821545d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db41-7745-b0ad-5affc821545d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db41-708b-b681-b9061e2f44d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019eb20b-db41-7745-b0ad-5affc821545d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db41-708b-b681-b9061e2f44d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_PerformanceBasedShareUnitsPSUsMember_019eb20b-db41-7049-8695-4a91dfcd8ec2" xlink:href="nvcr-20260630.xsd#nvcr_PerformanceBasedShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019eb20b-db41-708b-b681-b9061e2f44d7" xlink:to="loc_nvcr_PerformanceBasedShareUnitsPSUsMember_019eb20b-db41-7049-8695-4a91dfcd8ec2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019eb20b-db41-7987-8ec2-afd2d6f658a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-782a-b9ec-7bc086752b28" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019eb20b-db41-7987-8ec2-afd2d6f658a0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019eb20b-db41-7975-aec3-12dadf9357ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019eb20b-db41-782a-b9ec-7bc086752b28" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019eb20b-db41-7975-aec3-12dadf9357ab" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/BasicanddilutednetincomelossperordinaryshareDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#BasicanddilutednetincomelossperordinaryshareDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/BasicanddilutednetincomelossperordinaryshareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019eb20b-db41-7e2f-ae5d-5586adc103b2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019eb20b-db41-75d3-89b7-f7407f9a0a42" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019eb20b-db41-7e2f-ae5d-5586adc103b2" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019eb20b-db41-75d3-89b7-f7407f9a0a42" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019eb20b-db41-7569-a174-56e7f2c75532" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019eb20b-db41-75d3-89b7-f7407f9a0a42" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019eb20b-db41-7569-a174-56e7f2c75532" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019eb20b-db41-7569-a174-56e7f2c75532_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019eb20b-db41-7569-a174-56e7f2c75532" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019eb20b-db41-7569-a174-56e7f2c75532_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019eb20b-db41-75e0-912e-938d43a6d9e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019eb20b-db41-7569-a174-56e7f2c75532" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019eb20b-db41-75e0-912e-938d43a6d9e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_019eb20b-db41-7f29-a69f-b973ccd2a711" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019eb20b-db41-75e0-912e-938d43a6d9e0" xlink:to="loc_us-gaap_EmployeeStockOptionMember_019eb20b-db41-7f29-a69f-b973ccd2a711" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_RestrictedStockUnitsRSUsAndPerformanceBasedShareUnitsPSUsMember_019eb20b-db41-7a22-9ce9-c26920368ea6" xlink:href="nvcr-20260630.xsd#nvcr_RestrictedStockUnitsRSUsAndPerformanceBasedShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019eb20b-db41-75e0-912e-938d43a6d9e0" xlink:to="loc_nvcr_RestrictedStockUnitsRSUsAndPerformanceBasedShareUnitsPSUsMember_019eb20b-db41-7a22-9ce9-c26920368ea6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_019eb20b-db41-7b69-94db-1cbffda43c47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019eb20b-db41-75e0-912e-938d43a6d9e0" xlink:to="loc_us-gaap_EmployeeStockMember_019eb20b-db41-7b69-94db-1cbffda43c47" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019eb20b-db41-78fe-bcfa-cd07c9ef8a11" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019eb20b-db41-7e2f-ae5d-5586adc103b2" xlink:to="loc_us-gaap_NetIncomeLoss_019eb20b-db41-78fe-bcfa-cd07c9ef8a11" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019eb20b-db41-7515-9c4d-f9da010dffe6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019eb20b-db41-7e2f-ae5d-5586adc103b2" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019eb20b-db41-7515-9c4d-f9da010dffe6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019eb20b-db41-79ed-ab8c-0a5218b4babf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019eb20b-db41-7e2f-ae5d-5586adc103b2" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019eb20b-db41-79ed-ab8c-0a5218b4babf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019eb20b-db41-7149-8b57-57d42f7c90f6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019eb20b-db41-7e2f-ae5d-5586adc103b2" xlink:to="loc_us-gaap_EarningsPerShareBasic_019eb20b-db41-7149-8b57-57d42f7c90f6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019eb20b-db41-7a00-8ff8-27865c98c372" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019eb20b-db41-7e2f-ae5d-5586adc103b2" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019eb20b-db41-7a00-8ff8-27865c98c372" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.novocure.com/role/SUPPLEMENTALINFORMATIONScheduleofLonglivedAssetsbyLocationDetails" xlink:type="simple" xlink:href="nvcr-20260630.xsd#SUPPLEMENTALINFORMATIONScheduleofLonglivedAssetsbyLocationDetails"/>
  <link:definitionLink xlink:role="http://www.novocure.com/role/SUPPLEMENTALINFORMATIONScheduleofLonglivedAssetsbyLocationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019eb20b-db41-7564-84f0-7a0024a4bc2c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019eb20b-db41-783e-8869-7556e4717891" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019eb20b-db41-7564-84f0-7a0024a4bc2c" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019eb20b-db41-783e-8869-7556e4717891" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019eb20b-db41-743d-8d6d-19157d2a6453" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_019eb20b-db41-783e-8869-7556e4717891" xlink:to="loc_srt_StatementGeographicalAxis_019eb20b-db41-743d-8d6d-19157d2a6453" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb20b-db41-743d-8d6d-19157d2a6453_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019eb20b-db41-743d-8d6d-19157d2a6453" xlink:to="loc_srt_SegmentGeographicalDomain_019eb20b-db41-743d-8d6d-19157d2a6453_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019eb20b-db41-7aa6-b219-294489a147bd" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019eb20b-db41-743d-8d6d-19157d2a6453" xlink:to="loc_srt_SegmentGeographicalDomain_019eb20b-db41-7aa6-b219-294489a147bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019eb20b-db41-73fd-ba01-85ffd4ab32ea" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb20b-db41-7aa6-b219-294489a147bd" xlink:to="loc_country_US_019eb20b-db41-73fd-ba01-85ffd4ab32ea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CH_019eb20b-db41-7130-acd8-beb8c9718762" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_CH"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb20b-db41-7aa6-b219-294489a147bd" xlink:to="loc_country_CH_019eb20b-db41-7130-acd8-beb8c9718762" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_IL_019eb20b-db41-7aa2-a3a4-471a7ea975b1" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_IL"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb20b-db41-7aa6-b219-294489a147bd" xlink:to="loc_country_IL_019eb20b-db41-7aa2-a3a4-471a7ea975b1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nvcr_OthersCountriesMember_019eb20b-db41-726a-9300-92fc8e61452f" xlink:href="nvcr-20260630.xsd#nvcr_OthersCountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019eb20b-db41-7aa6-b219-294489a147bd" xlink:to="loc_nvcr_OthersCountriesMember_019eb20b-db41-726a-9300-92fc8e61452f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncurrentAssets_019eb20b-db41-7ad4-94da-d3ea5992f32e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_019eb20b-db41-7564-84f0-7a0024a4bc2c" xlink:to="loc_us-gaap_NoncurrentAssets_019eb20b-db41-7ad4-94da-d3ea5992f32e" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
