A discipline of masturbation characterized by extraordinary vigor and skill, as well as enormous genital peril. In trained hands, double fisted monkey style can form a glorious, balanced union between a man and his fingers. In untrained hands, it can lead to genital fracturing, inversion, or worse.
"Dude, Bob tried Double Fisted Monkey Style last night."
"Oh no! I warned him! Did he survive?"
"The hospital said he might eventually recover partial use of his legs. They dug his penis out of a tree two miles downwind."
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.