Meaning

• A hard-shelled seed.

  "There are many sort of nuts: peanuts, cashews, pistachios, Brazil nuts and more."

• A piece of metal, usually square or hexagonal in shape, with a hole through it having machined internal threads, intended to be screwed onto a bolt or other threaded shaft.

• A crazy person.

  "He was driving his car like a nut."

• The head.

• Monthly expense to keep a venture running.

• The amount of money necessary to set up some venture; set-up costs.

• A stash of money owned by an extremely rich investor, sufficient to sustain a high level of consumption if all other money is lost.

• On stringed instruments such as guitars and violins, the small piece at the peghead end of the fingerboard that holds the strings at the proper spacing and, in most cases, the proper height.

• En, a unit of measurement equal to half of the height of the type in use.

• An extravagantly fashionable young man.

• (chiefly plural) A testicle.

  "I kicked him in the nuts."

• Semen, ejaculate.

• Orgasm, ejaculation; especially release of semen

  "He just needs a good nut to make him feel better."

• An extreme enthusiast.

  "a fashion nut"

• A shaped piece of metal, threaded by a wire loop, which is jammed in a crack in the rockface and used to protect a climb. (Originally, machine nuts [sense #2] were used for this purpose.)

• (only in attributive use) The best possible hand of a certain type, for instance: "nut straight", "nut flush", and "nut full house". Compare nuts.

  "nut flush = the best possible flush available"

• The tumbler of a gunlock.

• A projection on each side of the shank of an anchor, to secure the stock in place.

Meaning

• (mostly in the form "nutting") To gather nuts.

• To hit deliberately with the head; to headbutt.

• (mildly) To orgasm; to ejaculate.