treachery
[noun]
Synonyms: betrayal, disloyalty, double-dealing, duplicity, faithlessness, infidelity, perfidy, treason

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Antonyms: dependability, trustworthiness
Contrasted words: incorruptibility, reliability, probity, rectitude, uprightness, constancy, fidelity, loyalty, staunchness
Related Idioms: dirty pool, dirty work at the crossroads
Related Words: falseheartedness, falseness, double cross, double-dealing, sellout

[TahlilGaran] English Synonym Dictionary ▲

treach‧e‧ry /ˈtretʃəri/ noun (plural treacheries)
[Date: 1100-1200; Language: Old French; Origin: trecherie, from trechier, trichier; ⇒ trick¹]

1. [uncountable] behaviour in which someone is not loyal to a person who trusts them, especially when this behaviour helps that person’s enemies:
the treachery of those who plotted against the king

2. [countable usually plural] a disloyal action against someone who trusts you

[TahlilGaran] Dictionary of Contemporary English ▲