Englishunbeliever
noun
a Holy War against the unbelievers:
infidel, heretic, heathen, non-believer, atheist, non-theist, agnostic, pagan, nihilist, apostate, freethinker, dissenter, nonconformist;
disbeliever, sceptic, cynic, doubter, doubting Thomas, questioner, scoffer;
archaic paynim;
rare nullifidian.
▷antonyms believer.
unbeliever Oxford Dictionary of English