[treach.er.ous] adj (14c) 1: characterized by or manifesting treachery: perfidious
2. a: likely to betray trust: unreliable "a ~ memory" b: providing insecure footing or support "~ quicksand" c: marked by hidden dangers, hazards, or perils syn see faithless -- treach.er.ous.ly adv -- treach.er.ous.ness n