PERFIDIOUS
Per*fid"i*ous, a. Etym: [L. perfidious.]
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.
PERFIDIOUSLY
Per*fid"i*ous*ly, adv.
Defn: In a perfidious manner.
PERFIDIOUSNESS
Per*fid"i*ous*ness, n.
Defn: The quality of being perfidious; perfidy. Clarendon.
PERFIDY
Per"fi*dy, n.; pl. Perfidies. Etym: [L. perfidia, fr. L. perfidus
faithless; per (cf. Skr. para away) + fides faith: cf. F. perfidie.
See Faith.]
Defn: The act of violating faith or allegiance; violation of a
promise or vow, or of trust reposed; faithlessness; teachery.
The ambition and perfidy of tyrants. Macaulay.
His perfidy to this sacred engagement. DeQuincey.
PERFIT
Per"fit, a.