noun
doubter, unbeliever, cynic, questioner, infidel, heathen, freethinker, atheist, deist, agnostic, heretic, disbeliever, Pyrrhonist, pagan, anti-Christian, dissenter, latitudinarian, misbeliever, rationalist, profaner, materialist, positivist, nihilist, somatist, scoffer, apostate, blasphemer; see also cynic.