Definition of nut:
(n) :
a hard-shelled
seed; 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
"1971: My attorney was waiting in a bar around the corner. “This won't make the nut,†he said, “unless we have unlimited credit.† Hunter S. Thompson, Fear and Loathing in Las Vegas (Harper Perennial 2005, p. 11)"