Without faith or belief; not giving credit; unbelieving; especially, without religious faith or faith in the Christian religion; skeptical.Without faithfulness or fidelity; not keeping faith; not adhering to allegiance, vows, or duty; disloyal: as, a faithless subject; a faithless servant; a faithless husband or wife.Tending to disappoint or deceive; deceptive; delusive.Synonyms and False, untruthful, perfidious, treacherous.