From Longman Dictionary of Contemporary Englishinfidelityin‧fi‧del‧i‧ty /ˌɪnfəˈdeləti/ noun (plural infidelities) [countable, uncountable] UNFAITHFULwhen someone has sex with a person who is not their wife, husband, or partner marital infidelity
Examples from the Corpus
infidelity• a marriage destroyed by infidelity• Her husband never knew of her infidelity.• There had been rumours for a long time of Clinton's marital infidelity. 