not adhering to allegiance, promises, vows, or duty

the faithless behavior of Benedict Arnold.

not trustworthy; unreliable.

without trust or belief.

being without religious faith.

(among Christians) bereft of Christian faith.

adjective

believing , faithful , constant , loyal , reliable , true

adjective

capricious , changeable , changeful , cheating , deceitful , dishonest , double-crossing , double-dealing * , doubting , dubious , false , fickle , fluctuating , inconstant , perfidious , recreant , skeptical , traitorous , treacherous , two-faced * , two-timing , unbelieving , unconverted , unfaithful , unloyal , unreliable , unstable , untrue , untrustworthy , untruthful , wavering , disloyal , false-hearted , atheist , deceptive , disaffected , false. unfaithful , hollow , incredulous , punic , shifting , unjust