treacherous

[trech-er-uhs]

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

/ ˈtrɛtʃərəs /

adjective

1. betraying or likely to betray faith or confidence

2. unstable, unreliable, or dangerous

   treacherous weather

   treacherous ground

Other Word Forms

• treacherousness noun
• treacherously adverb
• untreacherous adjective
• untreacherousness noun

Word History and Origins

Origin of treacherous¹

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”

Related Words

• difficult 
• hazardous 
• icy 
• ominous 
• perilous 
• precarious 
• risky 
• slippery 
• ticklish 
• tricky 
• unreliable 
• unsafe 
• unstable