unbelievingEnglishOxford American Thesaurusunbelieving adjective they were to preach to the unbelieving people: faithless, nonbelieving, agnostic, atheistic, nontheistic, heathen, pagan, infidel, irreligious, unenlightened; disbelieving, doubting, doubtful, skeptical, cynical, unconvinced, incredulous. ▷antonyms believing.