This is slang for masturbating, the short way of saying it. Also the less embarrassing way of saying masturbating when speaking around adults and strangers.
ex. I caught him m.bating two times!
ex. I really enjoy a m.bating in the afternoon.
A variant of the slang term "Omning it" popularised by the TV show invincible. Used in reference to when someone is masturbating and reaches such an intense point that they start heating up, hence them "baking" up. Usually followed by someone letting it crust in the intense heat, baking their semen.
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.