perfidy

1 lack of faithfulness especially to one's husband or wife <he decided to forgive his wife's perfidy, choosing to ascribe it to a moment of uncharacteristic weakness> Synonyms disloyalty, faithlessness, falseness, falsity, inconstancy, perfidiousness, infidelity, unfaithfulnessRelated 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 full cost—both in compromised intelligence and in human life—of the double agent's perfidy is not yet known> Synonyms backstabbing, business, disloyalty, double cross, faithlessness, falseness, falsity, infidelity, betrayal, sellout, treachery, treason, two-timing, unfaithfulnessRelated 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