faithless

adjective

1 she left her faithless lover:

unfaithful, disloyal, inconstant, false, false-hearted, untrue, adulterous, traitorous, treacherous, perfidious, fickle, flighty, untrustworthy, unreliable, undependable, deceitful, deceiving, two-faced, Janus-faced, double-dealing, double-crossing;

informal cheating, two-timing, backstabbing;

rare double-faced.

▷antonyms faithful.

2 the natives were ungodly and faithless:

unbelieving, nonbelieving, irreligious, without religious faith, disbelieving, doubting, skeptical, agnostic, atheistic, nontheistic;

pagan, heathen;

rare nullifidian.