adj. 25B6; adjective
her faithless lover : UNFAITHFUL, disloyal, inconstant, false, untrue, adulterous, traitorous; fickle, flighty, untrustworthy, unreliable, undependable; deceitful, two-faced, double-crossing; informal cheating, two-timing, back-stabbing; poetic/literary perfidious.
the natives were faithless : UNBELIEVING, non-believing, irreligious, disbelieving, agnostic, atheistic; pagan, heathen; rare nullifidian.