[ trech-er-uhs ]
/ ˈtrɛtʃ ər əs /


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 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Examples from the Web for treacherously

British Dictionary definitions for treacherously

/ (ˈtrɛtʃərəs) /


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

Derived forms of treacherous

treacherously, adverbtreacherousness, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012