NUT

noun

1. A hard-shelled seed.
2. 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.
3. A crazy person.

verb

1. (mostly in the form "nutting") To gather nuts.
2. To hit deliberately with the head; to headbutt.
3. (mildly) To orgasm; to ejaculate.