Guilty of perfidy; violating good faith or vows; false to trust or confidence reposed; teacherous; faithless; as, a perfidious friend.

tending to betray; especially having a treacherous character as attributed to the Carthaginians by the Romans; "Punic faith"; "the perfidious Judas"; "the fiercest and most treacherous of foes"; "treacherous intrigues"

Involving, or characterized by, perfidy.