When I found out that Taylor Kitsch is playing Gambit in the new X-Men movie, I fan-girled for the first time ever.
Scene: Me and Jill watching TV.
Jill: Ooh X-Men preview! I wonder if Tim Riggins is Gambit.
Me: TIM RIGGINS?!?! WHAT?!
Jill: He's in the new X-Men movie.
Me: HE'S IN THE NEW X-MEN MOVIE?!?!?!
Jill: *surprised I don't already know this* Yeah... just watch.
Taylor Kitsch: *appears on screen during X-Men commercial*
Me: EEEEEEEE!!!!!! *hands flailing*
Jill: I have you never seen you fangirl before. It's quite amusing.
Now I "geek out" over many things: Survivor, Lord of the Rings, Arrested Development, Harry Potter, and more recently Star Trek. "Geeking out" involves knowing way too many facts about, being able to quote entire scenes from, dressing up as, posting on message boards about, dropping random quotes from...and many other things that indicate very high interest in a book, tv show, movie, or person. It may be exceedingly nerdy, but it's all very calm and orderly. But fangirling is much, much different. In addition to everything listed above, it involves squeeling, ALLCAPS, poor grammar and exclamation points. It is loud, insane, highly mockable, and in some instances can be scary. (See: TwiMoms.) For laid-back people like myself, "geeking out" is much preferred. Fangirls are to be pointed at while laughing.
BUT OMG TIM RIGGINS IS GAMBIT!!!!!
(And if you do not know who Tim Riggins is, I feel great pity for you.)