Treehat (noun) is used to describe someone who has a broccoli-style haircut. Mostly used to roast someone who gets no bitches. This roast originated from an episode on the show bigtime rush, where some of the characters are seen wearing a hat with a tree on it.
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.