A filthy man who thinks his idiocy attracts women. Usually fat women will tolerate his stupor, and are willing to sleep with him.
"Haha, look at that krum bum hitting on Shamoo!"
"I heard krum bum tried to stick his penis in some 400lbs chick's belly button thinking it was her vagina!!!"
It is said of the situation where a person has the bad luck to make contact with his testicles against an undefined surface or object, intentioned or not.
Given the nature of the word, it is more appropriate to design cases where the interaction is made with a moving object, for example, a ball.
Although it is extremely painful for the victim, it tends to be considerably funny to people who witness it.
Today in the baseball game the pitcher took a nutshot; the baseball hit him in the nuts.
Man, I just watched the funniest nutshot video ever.