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
Derived 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.
Kym and sister-in-law Kirsten Swanson McGillicuddy, flew out to join the search but it was put on hold due to treacherous weather conditions.
From BBC • Jun. 4, 2026
Recalling one such journey, islander Tony Usman said "it was very scary", as the poor weather made the transfer from a small boat to the ferry treacherous.
From Barron's • May 18, 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
Is there a treacherous part of me that’s pissed off and sad that she didn’t kick me awake and damn the consequences?
From "The Cruel Prince" by Holly Black
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.
