Synonyms for Nut:

n.

bur, bolt, cervical, cojones, bits, cap, beaver, cervix, bollocks. eccentric, fanatic, pin, nail, dowel, butterfly nut, plug, rivet. central nervous system, cranium, brainstem, cerebral cortex, cerebral, brain death, brain cell, head, brain damage, cerebellum, crown, skull, brainwave, brain. ding-a-ling, nutjob, headcase, loon, weirdo, weirdie, space cadet, dingbat, madwoman, loony, wise, cuckoo. prune, peppercorn, sultana, bug, concern, raisin. conk, body, noggin, poll, pate, noddle, bean, noodle, block. authority (noun)
connoisseur.
crazy, overenthusiastic person (noun)
eccentric, loony, fanatic, crackpot, crank, lunatic, maniac, fiend, freak, screwball, zealot.
eccentric person (noun)
kook.
enthusiast (noun)
buff, zealot, fancier, enthusiast, fiend, addict, patron, freak, connoisseur, aficionado, supporter, devotee, fan.
lunatic (noun)
kook, lunatic, neurotic, madman, crank, psychopath, maniac, crazy, psychotic, crackpot.
nut (noun)
beechnut, addict, filbert, screwball, ball, egg, crank, acorn, bollock, coconut, peanut, en, testis, nut case, almond, hazelnut, freak, nutcase, orchis, fruitcake, chestnut, pine nut, butternut, pecan, ballock, walnut, crackpot, cashew, brazil nut, pistachio.
problem (noun)
burden, difficulty, responsibility.
seed of fruit, vegetable (noun)
stone, kernel.

Other synonyms:

cuckoo, raisin, dowel, pate, noggin, cranium, bolt, peppercorn, noddle, ding-a-ling, fruit, conk, noodle, head, butterfly nut, weirdo, weirdie, dingbat, loon. sultana, poll, skull, rivet. prune, loony. nail, bean. fanatic. bug. plug, pin. crown, block. grain
kernel.
prickly
bur.

Usage examples for nut

  1. Grey, of all shades, from light blue to butter- nut was the universal colour. – Stonewall Jackson And The American Civil War by G. F. R. Henderson
  2. Thy pretious Iliads lock'd up in a nut – Lucasta by Richard Lovelace