When you're discussing something geeky very intensely.
When you know a lot of information about something unusual, usually nerdy, and express it with greatenthusiasm.
Bruce: Batman never killed his villains until Robin died, which is the only reason why people began to call him 'The Dark Knight'. And in the series 'The Dark Knight Returns', Robin was a girl after Jason died.
Wayne: Dude, relax. I only said I was excited for The Dark Knight.
Bruce: Sorry, I was nerding out for a minute there.
When someone takes something so far that it becomes nerdy. This happens in a couple of ways:
1: is when someone defines or corrects you with dictionary like precision.
2:When someone makes somethign that should be simple and makes it into something really complex by adding longgggg ass names to it
Guy : "Hey, let's go jump off that diving board"
Nerd: " Watch me do a triple backflip while rotating at 2.4 m/s at 57 degrees south of west, and land in the water creating a splash radious of exactly 3.4256 meters...."
Guys: " Uh.... nvm this guy is nerding it up, peace "
When your talking to a person and they start going off about a comic book hero or video game and all you can do is nod and pretend you understand what they are saying
Girl 1: Hey! how was your weekend?
Girl 2: Oh fun. i was busy dodging lightning bolts in the thunder plains
Girl 3: wha...?
Girl 2: Oh you see i have to dodge them 200 times in order to get the venus sigil and... (blah blah blah)