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.
What the pair found was a desert highway that rolls up and down, like an asphalt serpent, with deadly blind peaks and treacherous hidden troughs.
From Barron's • Mar. 8, 2026
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
According to Curtis, the discovery coincides with 30 years since the Sea Empress oil spill, highlighting how "treacherous" Pembrokeshire waters can be.
From BBC • Feb. 17, 2026
And, most treacherous of all, they still had to bring down Hale.
From "Killers of the Flower Moon" by David Grann
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.
