to squeal or behave like a teenager, no matter your actual age, in response to anything Twilight/Edward/Rob Pattinson related. May also cause shaking, crying, shortness of breath, spontaneous Robgasm, or Jizzing your pants.
I completely fangirled when I saw the pictures of Rob Pattinson as shirtless Edward in New Moon.
The act of fanning ones hands rapidly near ones face in overwhelming excitement as a fangirl would when meeting her obsession.
I fangirled when I found myself standing next to Nick Lachey at Starbucks!