The term "Undead" or "Living Dead" is used when referring to creatures that are in actuality dead, but seem to be alive and in a trance. The term can also mean someone who is only sort of alive. Living in the sense that they are able to walk and eat, but only instinctively. However this is not always the case either, as with a ghost, the only thing dead is the body itself, but the spirit is still living.
The term is used to apply to Ghosts, Zombies, Vampires and Mummies. Although some Vampires and Zombies are not mindless and walk around as if in a trance. Some, such as Solomon Grundy and Dracula, a zombie and vampire, actually appear to possess souls, but presumably this is merely a supernatural illusion.