Per*fid"i*ous (pər*fid"i*us; 277), a. [L. perfidious.]
Guilty of perfidy; violating good faith or vows; false to trust or confidence reposed; teacherous; faithless; as, a perfidious friend. Shak.
Involving, or characterized by, perfidy. "Involved in this perfidious fraud." Milton.
© Webster 1913