-rē, -ri noun
( -es )
Etymology: Middle English trecherie, tricherie, from Old French, from trechier, trichier to trick, cheat, deceive + -erie -ery
1.
a. : violation of allegiance or of faith and confidence : betrayal of trust : treason
to oppose … the party organization would be regarded by most members as little short of treachery — R.M.Dawson
b. : an instance of treachery : an act of perfidy or treason
blackmail the colonel into one of the greatest treacheries of history — Fletcher Pratt
2. : something treacherous ; specifically : something that is or is likely to be unstable or unreliable