UNFAITHFULwhen someone has sex with a person who is not their wife, husband, or partner 〔对丈夫、妻子或伴侣的〕不贞行为
marital infidelity
对婚姻的不忠诚
Examples from the Corpus
infidelity• a marriagedestroyed by infidelity• Her husband never knew of her infidelity.• There had been rumours for a long time of Clinton's maritalinfidelity.