Unfaithful, disloyal, treacherous.

Treasonable; traitorous, perfidious.

Characterized by perfidy; guilty of breaking faith or violating confidence; deliberately faithless; treacherous. Also occasionally as n.: a…

Originally Scottish. Unfaithful, disloyal, perfidious. Obsolete (archaic in later use).

Pledge-breaking, faithless, perfidious. Also as n. with the: promise-breakers as a class.

= false-hearted adj. at compounds 1b.

= perfidious, adj.