disloyal

/(ˌ)dis-ˈlȯi(-ə)l/

Middle English, from Anglo-French desleial, desloial, from des- dis- + leal loyal

adjective

  1. lacking in loyalty; also : showing an absence of allegiance, devotion, obligation, faith, or support

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.