adjective treach·er·ous \ˈtre-chə-rəs, ˈtrech-rəs\

: not able to be trusted : showing that someone cannot be trusted

: very dangerous and difficult to deal with

Full Definition of TREACHEROUS

:  characterized by or manifesting treachery :  perfidious
a :  likely to betray trust :  unreliable <a treacherous memory>
b :  providing insecure footing or support <treacherous quicksand>
c :  marked by hidden dangers, hazards, or perils
treach·er·ous·ly adverb
treach·er·ous·ness noun


  1. a treacherous act of betrayal
  2. They were not prepared to hike over such treacherous terrain.
  3. The snow made their hike all the more treacherous.
  4. Discussions about money can lead couples into treacherous territory.

First Known Use of TREACHEROUS

14th century

Synonym Discussion of TREACHEROUS

faithless, false, disloyal, traitorous, treacherous, perfidious mean untrue to what should command one's fidelity or allegiance. faithless applies to any failure to keep a promise or pledge or any breach of allegiance or loyalty <faithless allies>. false stresses the fact of failing to be true in any manner ranging from fickleness to cold treachery <betrayed by false friends>. disloyal implies a lack of complete faithfulness to a friend, cause, leader, or country <disloyal to their country>. traitorous implies either actual treason or a serious betrayal of trust <traitorous acts punishable by death>. treacherous implies readiness to betray trust or confidence <a treacherous adviser>. perfidious adds to faithless the implication of an incapacity for fidelity or reliability <a perfidious double-crosser>.


TREACHEROUSLY Defined for Kids


adjective treach·er·ous \ˈtre-chə-rəs\

Definition of TREACHEROUS for Kids

:  not safe because of hidden dangers <This was a treacherous road at night … — John Reynolds Gardiner, Stone Fox>
:  not trustworthy :  guilty of betrayal or likely to betray <a treacherous enemy>
treach·er·ous·ly adverb


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