- Treachery is a betrayal of trust.
An example of treachery is when you cheat on your wife with her best friend.
treachery definition by Webster's New World
- betrayal of trust, faith, or allegiance; perfidy, disloyalty, or treason
- an act of perfidy or treason
Origin: Middle English trecherie ; from Old French tricherie, trickery ; from trichier, to cheat: see trick
treachery definition by American Heritage Dictionary
noun pl. treach·er·ies
- Willful betrayal of fidelity, confidence, or trust; perfidy.
- The act or an instance of such betrayal.
Origin: Middle English trecherie, from Old French, from trichier, to trick, probably from Vulgar Latin *triccāre; see trick.