Synonyms of unbelievers

2 Syllables
atheist, heathen, scoffer, pagan, doubter, cynic
3 Syllables
agnostic, profaner, questioner, dissenter, heretic, freethinker, infidel, nihilist, pessimist
4 Syllables
nonbeliever, misbeliever, disbeliever, misanthrope, materialist, rationalist, apostate