fanaticEnglishOxford American Thesaurusfanatic noun 1 a religious fanatic: zealot, extremist, militant, dogmatist, devotee, sectarian, bigot, chauvinist, partisan, radical, diehard, ultra, activist, apologist, adherent; visionary; informal maniac, crank, freak; US, informal wackadoo, wackadoodle. ▷antonyms moderate. 2 informal a keep-fit fanatic: enthusiast, fan, devotee, lover, addict; informal nut, maniac, fiend, freak, junkie, bug, crank, buff, -head, a great one for; North American, informal geek, jock.