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Synonyms

treacherous

American  
[trech-er-uhs] / ˈtrɛtʃ ər əs /

adjective

  1. characterized by faithlessness or readiness to betray trust; traitorous.

    Synonyms:
    treasonous, faithless, unfaithful
    Antonyms:
    loyal

  2. deceptive, untrustworthy, or unreliable.

    Synonyms:
    deceitful
    Antonyms:
    reliable

  3. unstable or insecure, as footing.

  4. dangerous; hazardous.

    a treacherous climb.
treacherous British  
/ ˈtrɛtʃərəs /

adjective

  1. betraying or likely to betray faith or confidence

  2. unstable, unreliable, or dangerous

    treacherous weather

    treacherous ground
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

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”

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.