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

Derived Forms

• ˈtreacherousness, noun
• ˈtreacherously, adverb

Other Words From

• treach·er·ous·ly adverb
• treach·er·ous·ness noun
• un·treach·er·ous adjective
• un·treach·er·ous·ness 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

Huge metal containers – broken free from their articulated lorries – rested at unfathomable angles amid a jumble of cars, crumpled furniture and treacherous mud.

From BBC

Thursday, when Gov. Gavin Newsom declared a state of emergency in Ventura County to mobilize resources to combat the treacherous blaze.

From Los Angeles Times

The pilot of a small plane that crashed on Santa Catalina Island, killing five, was warned not to take off in treacherous conditions after dark.

From Los Angeles Times

Max Verstappen produced a superb drive to win the Sao Paulo Grand Prix on Sunday, coming through the field from 17th on the grid in treacherous conditions.

From BBC

In treacherous conditions, Verstappen was in a league of his own, putting in a drive that underlined why he is regarded by so many in Formula 1 as the best driver in the world.

From BBC

Related Words

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