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
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”
Explanation
Treacherous means either not trusted or dangerous. A treacherous road might be icy or otherwise likely to cause a car accident. A treacherous friend will betray you. Treachery refers to harmful acts you might do to someone who trusts you. It can also refer to being disloyal to your native country, but the word treason is more common in this sense. Treachery is from Middle English trecherie, from Old French, from trichier "to trick or cheat." The English word trick is from trikier, a slightly different spelling that was used in some dialects of Old French.
Vocabulary lists containing treacherous
List 2
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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.
The Ikner case is different, and that difference is precisely what makes it so legally treacherous.
From Barron's • May 11, 2026
Although only 30 people had made it to the gig because of the treacherous weather conditions, the hotel’s booker had seen enough: He offered the Stones a regular gig.
From Los Angeles Times • Apr. 20, 2026
In retrospect, its uncompromising litmus tests and chilly demeanor were real weaknesses, creating a pervading fear that any false step could expel one from good graces, and that a return trip was always, always treacherous.
From Slate • Apr. 13, 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
He was friendly, in a treacherous sort of way, smiling into one’s face the while he meditated some underhand trick, as, for instance, when he stole from Buck’s food at the first meal.
From "The Call of the Wild" by Jack London
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.
