When you find out some unknown piece of information, and you feel a rush of Intellectual glee. Related to intellectual masturbation, and Brain Jizzing

An orgasm of the brain, something that would be the equivalent of information sex, something that would make a nerd smile in a kind of creepy, happy way.

The sudden, and often timely, understanding of a subject, usually in school. Most commonly paired with a loud exclamation of "OHHHHHHHHHHH! I GET IT NOW!" or something very similar. Usually done by the less studious members of the class, who understand it right before a test or quiz.

A sudden rush of short-lived intellect, intelligence, or insight on a matter or idea.

When your brain finally figures out something that was on the tip of your tongue (i.e. an eighties song or the name of a movie, etc.) and you end up yelling it at a random moment after the fact that is at a point of time that has nothing to do with the thing that you remembered !!

It is a type of orgasm acheived from mind. Sexual arousal is physical and mental—but if one tries hard enough, our thoughts really are all we need to get off.
Some people can actually ‘think’ themselves off through fantasy and breath work.
These are sometimes called “energy orgasms,” because the method requires developed brains. Orgasms from “thinking off” show up in the same spot of the brain as orgasms from genital contact.

Brain fantasies