isr.co.ro : glossary MOO (MUD, Object Oriented) A type of computer-mediated, interactive, virtual environment that's become popular both for recreation and educational applications. Essentially, MOOs allow ordinary players to add their own rooms and other constructs to the regular pre-set rooms, characters, objects, and rules that make up a standard MUD (Multi-User Dungeon/Dimension), the larger class of computer-mediated virtual worlds that includes MOOs and several other variations.