To remove one's shirt while under the influence of alcohol. Experienced, more aggressive clusers frequently tear off their shirt, rather than taking it off.
"How was your night last night? I could tell you were pretty hammered."
"I'm not sure, but I woke up with my lacoste shirt torn in half. I must have been clusing real hard."
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.