UNFAITHFULsomeone who is married and has sex with someone who is not their wife or husband 通奸者;奸夫;奸妇
Examples from the Corpus
adulterer• Jefferson was called a traitor, and Andrew Jackson was accused of being a drunken, ignorantadulterer.• It is the sort of hotel that has a skeleton in every closet and a registerthick with the pseudonyms of adulterers.• Pre-election talk about cutting off thieves' hands and stoningadulterers is no longer heard.