A slang term, used in place of the more "correct" term for ejaculation. The term originated from when sperm would bust from the testicles (nuts). Not to be confused with "bust your nuts" meaning to smash the testicles.
"My roomate tried to steal my girl last night, so I bust a nut on his bed."
When one, usually with little impulse control, cannot help himself hold back cumming. When a guy jerks off and then ejaculates, usually in a short period of time, having been highly aroused.
I was so horny, I couldn't help but bust a nut in my pants, while looking at that hot chick.
"A complete douche bag who is also a dumbass. This word was invented by Jimmy, and became a fad at his school, although no one but him and Crake knew what it meant." thinks Snowman.