From Longman Dictionary of Contemporary Englishtreacherytreach‧e‧ry /ˈtretʃəri/ noun (plural treacheries) 1 [uncountable]BETRAY 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 king2 [countable usually plural]BETRAY a disloyal action against someone who trusts you
Examples from the Corpus
treachery• The inadequacy and treachery of the old leaderships of the working class have made the need all the more imperative.• Selling military secrets is an unforgivable act of treachery.• The existence of treachery finds confirmation elsewhere.• There is a fear of treachery.• After a furious argument during which he accused the prime minister of treachery, he announced that he would resign his Cabinet position.• There followed a swingeing series of letters between Rodrigo and Berenguer, in which each accused the other of treachery and cowardice.• The King went back to the palace planning treachery against the heroes and vowing they should never have the Golden Fleece.• When the king learned of his brother's treachery, he quickly ordered his execution.• As nothing else, the child within her womb kept reminding her daily, hourly of the treachery she had perpetrated.• For many battered women the unpredictable treachery of a deadly serpent is an apt characterization of the abusive actions of their husbands.Origin treachery (1100-1200) Old French trecherie, from trechier, trichier; → TRICK1 