When you're discussing something geeky very intensely.
When you
know a lot of information about something unusual, usually nerdy, and
express it with great
enthusiasm.
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.