Someone who is obsessed with a particular tv show, book series, video game, or other mainstream entertainment -- typically of the sci-fi/fantasy genre -- to the point where they will collect every marketable product available related to the SBG (show/book/game) which they can afford. They will defend their obsession vigorously, even violently, against fans of other SBG's, or even against fans of the same SBG who ask them to even consider the remote possibility that the SBG has any kind of flaw whatsoever. Frequently seen in chat rooms or Internet message boards posting in incomplete sentences and swearing a lot.

Fangirls have been theorized to exist, but have never been seen in the wild.