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treacherous

TRECH-er-us /ˈtrɛtʃərəs/

adjectiveB2GRESATACTTOEFLIELTS

generalliterary

Presenting hidden or unpredictable dangers; untrustworthy or deceitful.

Emphasizes deceptive appearance—something looks safe or manageable but harbors lethal traps.

The story behind the word. Emerging in Middle English from Old French 'tricher' (to cheat or trick), treacherous originally described deceitful people who broke promises. Over time, travelers applied it to mountain trails that 'tricked' you into taking a fatal step.

Word relationships

perilous: Perilous means full of open danger; treacherous implies hidden or deceptive danger.
precarious: Precarious refers to instability or likelihood of falling; treacherous implies actively hazardous conditions.

safe: Free from danger or risk.
reliable: Dependable and free from hidden flaws or surprises.

Commonly confused with

traitorous: Traitorous involves disloyalty to country or person; treacherous can apply to people OR physical hazards like icy paths.

Word family

treachery (noun): Violation of faith, betrayal of trust, or hazardous deceptiveness.
treacherously (adverb): In a hazardous or deceitful manner.

Collocations

treacherous terrain
treacherous conditions
treacherous ice
treacherous path

Idioms & expressions

skating on thin ice

Example sentences

"The snow covered a layer of black ice, making the high mountain pass treacherous for the rescue vehicle." Alpine hazard
"Navigating the treacherous political climate of the border zone required extreme caution." Deceitful conduct

Memory hook

TREACHEROUS paths drop TRICKS on your TRIPS. Deceptively dangerous.

When not to use

Do not use for obvious, visible hazards like a bright warning fire; reserve for deceptive risks.

Fun facts

Dante's Inferno places treacherous betrayers in the lowest, ninth circle of Hell—a lake of solid ice.