Pronunciation : Per*fid"i*ous Part of Speech : a. Etymology : [L. perfidious.] Definition : 1. Guilty of perfidy; violating good faith or vows; false to trust or confidence reposed; teacherous; faithless; as, a perfidious friend. Shak.
2. Involving, or characterized by, perfidy. "Involved in this perfidious fraud." Milton. Source : Webster's Unabridged Dictionary, 1913