Someone who is litterally obsessed with all concepts of Harry Potter. Usually, they have read all of the books at LEAST three times, they read/write fanfictions to it, and all thoughts are centered around it. Some even masturbate to Harry Potter and it's characters...
"Dude, what the hell are you doing?"
"Reading the fifth Harry Potter book."
"You are such a Harry Potter Fag!"
"So? hey, do you know where the lotion is...?"