What does undead mean?

Undead is a term used in fantasy and horror genres to refer to creatures that are once living beings but have died and returned to life in some form. Undead creatures are often depicted as being animated by dark magic, necromancy, or even divine forces. They may retain some of their original physical form but are usually in a state of decay or decomposition, and their behaviour and motivations are often vastly different from when they were alive. Common examples include zombies, vampires, liches, and ghouls.