Per‐fid″i‐ous (pẽr‐fĭd″ĭ‐ŭs; 277), a. [L. perfidious.] 1. Guilty of perfidy; violating good faith or vows; false to trust or confidence reposed; treacherous; faithless; as, a perfidious friend. Shak.
2. Involving, or characterized by, perfidy. “Involved in this perfidious fraud.” Milton.