treacherous
Americanadjective
-
characterized by faithlessness or readiness to betray trust; traitorous.
- Synonyms:
- treasonous, faithless, unfaithful
- Antonyms:
- loyal
-
deceptive, untrustworthy, or unreliable.
- Synonyms:
- deceitful
- Antonyms:
- reliable
-
unstable or insecure, as footing.
-
a treacherous climb.
adjective
-
betraying or likely to betray faith or confidence
-
unstable, unreliable, or dangerous
treacherous weather
treacherous ground
Other Word Forms
- treacherously adverb
- treacherousness noun
- untreacherous adjective
- untreacherousness noun
Etymology
Origin of treacherous
First recorded in 1300–50; Middle English trecherous, from Anglo-French, equivalent to trecher “deceiver” ( trech(ier) “to deceive” + -er -er 2 ) + -ous -ous; compare French tricheur “trickster”
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
He has investigated the agendas of powerful fossil fuel billionaires, delved into epic feuds pitting some of the world's largest energy companies against each other, and revealed how drillers navigate a treacherous political landscape.
From The Wall Street Journal • Mar. 2, 2026
A 70-year-old man died Tuesday after falling from a cliff along California’s treacherous Devil’s Slide, an oceanside stretch in Pacifica known for steep terrain that has led to several fatal accidents.
From Los Angeles Times • Feb. 25, 2026
Six have been accounted for, but mountain rescue teams battling treacherous conditions were still trying to reach them while also looking for the others, as snow continued to fall and daylight faded.
From Barron's • Feb. 18, 2026
Woods will also face the mental pressure of long summit pushes, particularly navigating the treacherous icefall between Base Camp and Camp 1.
From BBC • Feb. 12, 2026
This was a treacherous road at night, but the moon was out and Searchlight could see well.
From "Stone Fox" by John Reynolds Gardiner
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
