treach·er·ous 
(trĕchər-əs)
(trĕchər-əs)adj.
1. Guilty of or characterized by betrayal of confidence or trust; perfidious.
2. Characterized by unforeseen or hidden hazards; dangerous or deceptive: treacherous waters; treacherous footing.
treacher·ous·ly adv.
treacher·ous·ness n.