The Collaborative International Dictionary of English v.0.48:

Nut \Nut\ (n[u^]t), n. [OE. nute, note, AS. hnutu; akin to D.
   noot, G. nuss, OHG. nuz, Icel. hnot, Sw. n["o]t, Dan.
   n["o]d.]
   [1913 Webster]
   1. (Bot.) The fruit of certain trees and shrubs (as of the
      almond, walnut, hickory, beech, filbert, etc.), consisting
      of a hard and indehiscent shell inclosing a kernel.
      [1913 Webster]

   2. A perforated block (usually a small piece of metal),
      provided with an internal or female screw thread, used on
      a bolt, or screw, for tightening or holding something, or
      for transmitting motion. See Illust. of 1st Bolt.
      [1913 Webster]

   3. The tumbler of a gunlock. --Knight.
      [1913 Webster]

   4. (Naut.) A projection on each side of the shank of an
      anchor, to secure the stock in place.
      [1913 Webster]

   5. pl. Testicles. [vulgar slang]
      [PJC]

   Check nut, Jam nut, Lock nut, a nut which is screwed up
      tightly against another nut on the same bolt or screw, in
      order to prevent accidental unscrewing of the first nut.


   Nut buoy. See under Buoy.

   Nut coal, screened coal of a size smaller than stove coal
      and larger than pea coal; -- called also chestnut coal.


   Nut crab (Zool.), any leucosoid crab of the genus Ebalia
      as, Ebalia tuberosa of Europe.

   Nut grass (Bot.), See nut grass in the vocabulary.

   Nut lock, a device, as a metal plate bent up at the
      corners, to prevent a nut from becoming unscrewed, as by
      jarring.

   Nut pine. (Bot.) See under Pine.

   Nut rush (Bot.), a genus of cyperaceous plants (Scleria)
      having a hard bony achene. Several species are found in
      the United States and many more in tropical regions.

   Nut tree, a tree that bears nuts.

   Nut weevil (Zool.), any species of weevils of the genus
      Balaninus and other allied genera, which in the larval
      state live in nuts.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Nut \Nut\, v. i. [imp. & p. p. Nutted; p. pr. & vb. n.
   Nutting.]
   To gather nuts.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nut
    n 1: usually large hard-shelled seed
    2: Egyptian goddess of the sky
    3: a small (usually square or hexagonal) metal block with
       internal screw thread to be fitted onto a bolt
    4: half the width of an em [syn: en, nut]
    5: a whimsically eccentric person [syn: crackpot, crank,
       nut, nut case, fruitcake, screwball]
    6: someone who is so ardently devoted to something that it
       resembles an addiction; "a golf addict"; "a car nut"; "a
       bodybuilding freak"; "a news junkie" [syn: addict, nut,
       freak, junkie, junky]
    7: one of the two male reproductive glands that produce
       spermatozoa and secrete androgens; "she kicked him in the
       balls and got away" [syn: testis, testicle, orchis,
       ball, ballock, bollock, nut, egg]
    v 1: gather nuts

Moby Thesaurus II by Grady Ward, 1.0:

184 Moby Thesaurus words for "nut":
   Brazil nut, English walnut, Macadamia nut, acorn, addict,
   aficionado, alien, aliene, almond, almond paste, amande,
   amande douce, amandes mondees, amateur, authority, bean, bedlamite,
   beechnut, ben nut, berry, betel nut, bigot, bird seed,
   bitter almond, black walnut, blanched almonds, bonduc nut,
   borderline case, bring in, buff, bug, burnt almond, butternut,
   candlenut, case, cashew, cashew nut, character, chestnut,
   chinquapin, cobnut, coconut, collector, conk, connoisseur,
   corozo nut, crackbrain, crackpot, crank, critic, crop, crop herbs,
   cuckoo, cumara nut, cut, dement, demon, demoniac, devotee, dig,
   dika nut, dilettante, ding-a-ling, dome, eager beaver, eccentric,
   energumen, enthusiast, erratic, expert, faddist, fan, fanatic,
   fanatico, fiend, flake, flaxseed, fou, freak, fruit, gather,
   gather in, glean, goober, goober pea, grabble, grain,
   great one for, ground-pea, groundnut, harebrain, harvest, hay,
   hayseed, head, hermit, hickory nut, hobbyist, hobo, horse chestnut,
   hound, idiot, infatuate, issue, kernel, kola, kola nut, kook,
   linseed, litchi nut, lone wolf, loner, loon, loony, lunatic,
   lunatic fringe, madman, maniac, maverick, meat, meshuggenah,
   monomaniac, mow, natural, nigger toe, noddle, noggin, noisette,
   noix, non compos, noncompos, nonconformist, noodle, odd fellow,
   oddball, oddity, original, outsider, palm nut, pariah, peanut,
   peanut butter, pecan, phrenetic, pick, pine nut, pip, pistachio,
   pit, pluck, poll, pundit, pursuer, queer duck, queer fish,
   queer specimen, question, rara avis, raving lunatic, reap,
   reap and carry, recluse, rhapsodist, salted peanuts, sassafras nut,
   savant, scholar, screwball, seed, solitary, souari nut, specialist,
   stone, strange duck, sucker for, sweet almond, technical expert,
   technician, tramp, type, visionary, walnut, weirdo, zealot