Synonyms and related words :
aliene, bedlamite, borderline case, character, crackbrain, crackpot, crank, dement, demoniac, eccentric, energumen, erratic, fanatic, flake, fou, freak, idiot, kook, loon, loony, lunatic, madman, maniac, meshuggenah, noncompos, nonconformist, nut, oddball, phrenetic, raving lunatic, recluse, screwball, strange duck