n A fastener: 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.
n (US|slagn) Financial term for monthly expense to keep a venture running.
n (US|slang) The amount of money necessary to set up some venture; set-up costs.
n (US|slang) A stash of money owned by an extremely rich investor, sufficient to sustain a high level of consumption if all other money is lost.
n (musical instruments) On string 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.
n (typography|_|slang)en | En, a unit of measurement equal to half of the height of the type in use.
n (context|historical|UK|_|slang) An extravagantly fashionable young man of the 1910s and 1920s.
n (context|vulgarity|slang|rarely used in the singular) A testicle.
n (climbing) 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.)
n (poker|only in attributive use) Relating to the nuts |nuts, the best possible hand on a given board.
v (UK|transitive|slang) To hit deliberately with the head; to headbutt.