Perfidious

PERFID'IOUS, adjective [Latin perfidus; per and fidus, faithful. Per in this word signifies through, beyond, or by, aside.]

1. Violating good faith or vows; false to trust or confidence reposed; treacherous; as a perfidious agent; a perfidious friend. [See [[Perfidy]].]

2. Proceeding from treachery, or consisting in breach of faith; as a perfidious act.

3. Guilty of violated allegiance; as a perfidious citizen; a man perfidious to his country.