From Longman Dictionary of Contemporary Englishadulterera‧dul‧ter‧er /əˈdʌltərə $ -ər/ noun [countable] UNFAITHFULsomeone who is married and has sex with someone who is not their wife or husband
Examples from the Corpus
adulterer• Jefferson was called a traitor, and Andrew Jackson was accused of being a drunken, ignorant adulterer.• It is the sort of hotel that has a skeleton in every closet and a register thick with the pseudonyms of adulterers.• Pre-election talk about cutting off thieves' hands and stoning adulterers is no longer heard. 