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.
The road ahead looks treacherous for Bass, the first sitting L.A. mayor to be forced into a runoff since 2005.
From Los Angeles Times • Jun. 10, 2026
The 24-year-old was one of seven participants who took part in the paddleboard tour when the group ran into difficulty while crossing a weir in "treacherous" conditions.
From BBC • Jun. 8, 2026
This is a lot more treacherous for those in, around or within a commutable distance of New York.
From The Wall Street Journal • 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
He’d salvaged boats that crashed in the treacherous Keys, and claimed the cargo—silver, furniture, silk, you name it.
From Full of Beans by Jennifer L. Holm
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.
