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.
Several trekkers and their guides say their journeys back down the mountains have been treacherous, taking up to three or four days and requiring them to pass collapsed roads and swept-away bridges.
From BBC ● Sep. 30, 2026
Nepal's mountain districts have seen persistent rain and snow in recent days, creating treacherous conditions for the country's economically important climbing tourism industry.
From BBC ● Sep. 27, 2026
According to the announcement, on Sunday a new MrBeast video will follow Donaldson and his crew as they attempt to survive “some of the most extreme and treacherous climates on Earth.”
From Los Angeles Times ● Sep. 3, 2026
Nepali rescue teams battled difficult terrain, an unpredictable river and treacherous marshland on Monday, the sixth day in their search for survivors and victims of devastating floods.
From Barron's ● Aug. 31, 2026
The climb of the sloping roof was extremely treacherous.
From "Redwall" by Brian Jacques
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Get a wordDefinitions 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.
