- characterized by faithlessness or readiness to betray trust; traitorous.
- deceptive, untrustworthy, or unreliable.
- unstable or insecure, as footing.
- dangerous; hazardous: a treacherous climb.
Origin of treacherous
SynonymsSee more synonyms on Thesaurus.com
Examples from the Web for treacherously
Trying to build a one-state reality in the name of “inalienable rights and realpolitik” is treacherously dishonest.Another Reason Dani Dayan is Wrong
Elisheva Goldberg, Sahar Segal
August 3, 2012
These are treacherously attacked one night by Finn's men, 1073.Beowulf
Yet of this, my only remaining comfort, I was treacherously and cruelly deprived.Gomez Arias
Joaqun Telesforo de Trueba y Coso
I will inform that lovely wife how treacherously you have acted.Beaux and Belles of England
He jumped backward, exclaiming that I had wounded him treacherously.The Memoires of Casanova, Complete
Jacques Casanova de Seingalt
I had you at my mercy when I was treacherously struck down from behind.Frank Merriwell's Pursuit
Burt L. Standish
- betraying or likely to betray faith or confidence
- unstable, unreliable, or dangeroustreacherous weather; treacherous ground
Word Origin and History for treacherously
early 14c., from Old French trecheros (12c.), from trecheur, agent noun from trechier "to cheat, trick" (see trick). Figuratively, of things, from c.1600. Related: Treacherously; treacherousness.