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English definition of “perfidious”

perfidious

adjective     /pəˈfɪd.i.əs/ US  /pɚ-/ literary
unable to be trusted, or showing no loyalty: She described the new criminal bill as a perfidious attack on democracy.Disloyalty, betrayal and treason
(Definition of perfidious adjective from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
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