Using treachery; violating allegiance or faith pledged; traitorous to the state or sovereign; perfidious in private life; betraying a trust.Marked by deceitfulness or perfidy; characteristic of a traitor.Having a good, fair, or sound appearance, but worthless or bad in character or quality; deceptive; not to be depended on or trusted.Synonyms Faithless, etc. (see perfidious), recreant, treasonable.