treacherous

[ trech-er-uhs ]
/ ˈtrɛtʃ ər əs /

adjective

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

1300–50; Middle English trecherous < Anglo-French, equivalent to trecher deceiver ( trech(ier) to deceive + -er -er2) + -ous -ous. Cf. French tricheur trickster

OTHER WORDS FROM treacherous

Example sentences from the Web for treacherously

British Dictionary definitions for treacherously

treacherous
/ (ˈtrɛtʃərəs) /

adjective

betraying or likely to betray faith or confidence
unstable, unreliable, or dangerous treacherous weather; treacherous ground

Derived forms of treacherous

treacherously, adverb treacherousness, noun