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

• treacherously adverb
• treacherousness noun
• 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”

Example Sentences

The conditions were treacherous, the session starting after heavy rain on a track wet enough for the extreme wet tyres, which nearly all drivers used throughout the first two sessions.

Read more on BBC

These are just a few of the treacherous episodes that have recently transpired at landfills in California, subjecting the state’s waste management industry to growing scrutiny by residents and regulators.

Read more on Los Angeles Times

But the deeper story is institutional: By narrowing inequality and widening access to opportunity, Nordic countries have made the climb less treacherous.

Read more on The Wall Street Journal

That’s when the roads became treacherous and often impassable with snow and ice.

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Despite the storm and the treacherous waters, Kontos, a skilled mariner, managed to guide his two boats to shelter in Antikythera’s only harbor, a small cove on its northern coast called Potamos.

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Related Words

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