Silly to the point of being waaaaay too silly to describe in words. Silly to the infinite degree. The pinnacle of silliness. Nirvana state of silliness.
"Man, that person running around on campus in a chicken outfit was acting mahaffee-silly". "She had so many Yeunglings that she was acting mahaffee-silly". "
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.