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English definition of “treacherous”

treacherous

adjective uk   /ˈtretʃ.ər.əs/ us    /-ɚ-/

treacherous adjective (DANGEROUS)

If the ground or sea is treacherous, it is extremely dangerous, especially because of bad weather conditions: Snow and ice have left many roads treacherous, and motorists are warned to drive slowly.

treacherous adjective (NOT LOYAL)

A person who is treacherous deceives someone who trusts them, or has no loyalty: Vargas plays the part of a treacherous aristocrat who betrays his king and country. I feel a bit treacherous to my own sex if I ever make general criticisms of women.
(Definition of treacherous from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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