Someone who is extremely obsessed with the Twilight saga and dedicates there lives to being exactally like the characters. The people who dress up and decorate themselfs with Twilight parafanalia. Usually fatt and ugly chicks who have no lives.
The Twihearts have their own section in most stores today
TwiHeart refers to a person who is unconditionally and irrevocably obsessed and in love with the Twilight Saga. This includes books and movies: Twilight, New Moon, Eclipse and Breaking Dawn. A Twiheart has read every book and seen the movies more than a dozen and a half times. A Twiheart also loves the Twilight Actors as much as they love the Characters themselves :) and yes the TwiHearts LOVE Twilight memorabilia!
That girls wearing a Team Edward shirt, you know shes a TwiHeart.