To over-react to something nerdy; a video game release, a new movie with a hot female celebrity envolved, etc.
P1"Dude, that girl is sooooo hot. I can't wait to see Scary Movie 4!"
P2"Have a dorkgasm over it at your own house!"
Geek: Pixar should join up with Studio Ghibli!
Geek: Dude, what was that?
Nerd: I just got a... dorkgasm!
(Example of a self-induced dorkgasm)
Loser: I love Trigun and I want to make a Warcraft III map out of it.
Examples of information-induced dorkgasms can be found at places like worldofwar.net and rpgamer.com
a.) graphing an interesting function on your graphing calculator.
b.) Laughing too heartily at a chemistry joke.
c.) Getting a discrete mathematics problem correct on the first try.