Video shows what infidelity means. Unfaithfulness in marriage: practice or instance of having a sexual or romantic affair with someone other than one's spouse, without the consent of the spouse.. Unfaithfulness in some other moral obligation.. Lack of religious belief.. infidelity synonyms: adultery, betrayal, faithlessness. Infidelity Meaning. How to pronounce, definition audio dictionary. How to say infidelity. Powered by MaryTTS, Wiktionary