Windbag

Meaning : someone who won't stop talking and is boring.

Usage : She's totally a windbag when it comes to talking about Harry Potter.

Dialog :

Tracie : Do you like Harry Potter?

Julie : I do love it! Deadly Hallows is my fav. Do you know when Harry .....

Jim (whispering to Tracie) : You just asked a stupid question. She's such a windbag while talking about Harry Potter.