To disappear from view at a speed that is un-noticeable. Watching an object that is receding into the distance at such a speed that you do not realise it is no longer there...
Staring at another person while on a heavy acid trip. The light around them fractures to the point where the dancing aurora meld into a kaleidoscopic hallucination and the subject slides into obliviocity.
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.