treacherous

/ˈtre-chə-rəs/

adjective

  1. likely to betray trust : unreliable

  2. providing insecure footing or support

  3. marked by hidden dangers, hazards, or perils

a treacherous memory

treacherous quicksand

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. false stresses the fact of failing to be true in any manner ranging from fickleness to cold treachery.