Ghouls are corpses of recently-killed prey reanimated by Vampires. They have little independence and are merely an extension of a true vampire's senses. They are not of the Fallen bloodlines. Particularly infamous ghouls include the Sidhe.
This is incorrectly applied to describe the offspring of a human and a vampire. In fact, vampires are sterile and the title is commonly claimed by the attention-seeking ghouls.