Mobile object

Mobile object, or "MOB", is the slang term given to any non-player character (NPC) or combatant in a video game. The term has been in use since the early days of online gaming, in the MUD community, then used in the more general sense that any NPC was a mob. The most common usage today is to refer to a monster, or a non-player enemy that may be hostile and can be killed for experience points or loot.