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

And while it’s giving them far too much credit, I have to wonder if there’s a ruthless, viciously humorous kind of satisfaction in watching two people become equals on the treacherous battlefield of unemployment.

From Salon

I was eager to see how criminals make these shady deals with potentially treacherous employees at a time when cyber-attacks around the world are becoming more impactful and disruptive to everyday life.

From BBC

What looked to be a treacherous start could be a turbo boost for a franchise heading into a stretch that includes the New York Giants, Miami Dolphins and Tennessee Titans, who are combined 0-6.

From Los Angeles Times

But officials warn that the trail is nonetheless treacherous.

From Los Angeles Times

Having survived the even more treacherous descent, Kirsty is thankful to have made it home unscathed.

From BBC

Related Words

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