unfaithfulness

1 lack of faithfulness especially to one's husband or wife he eventually forgave his wife's unfaithfulness Synonyms disloyalty, faithlessness, falseness, falsity, inconstancy, perfidiousness, perfidy, infidelityRelated Words adultery; betrayal, double-cross, double-dealing, duplicity, sellout, treachery, treason; deceit, deception, lyingNear Antonyms staunchness, steadfastness; dependability, reliability; honesty, trustworthinessAntonyms allegiance, constancy, devotedness, devotion, faith, faithfulness, fealty, fidelity, loyalty

2 the act or fact of violating the trust or confidence of another the jaw-dropping unfaithfulness of the person she had considered her best friend was deeply hurtful Synonyms backstabbing, business, disloyalty, double cross, faithlessness, falseness, falsity, infidelity, perfidy, sellout, treachery, treason, two-timing, betrayalRelated Words abandonment, desertion; deceit, deception, double-dealing, duplicity, guile, two-facedness; fraud, informing, lying, snitching, talebearing, trickeryNear Antonyms dependability, reliability, trustworthiness; defense, protection, safeguard, shieldAntonyms allegiance, devotion, faithfulness, fealty, fidelity, loyalty, staunchness, steadfastness

3 a sexual encounter or relationship between a married person and someone other than their spouse there were charges of unfaithfulness on both sides Synonyms cheating, infidelity, misconduct, two-timing, adulteryRelated Words criminal conversation; free love, promiscuity; disloyalty, faithlessness, falseness, inconstancy, perfidiousness, perfidy, treachery; affair (also affaire), amour, fling, love, love affair, romance; intrigue; attachment, infatuation; entanglement, flirtation; liaison, passionNear Antonyms allegiance, constancy, dedication, devotedness, devotion, fealty, loyalty, steadfastnessAntonyms faithfulness, fidelity