I have also heard it defined as Multi-Undergraduate Destroyer, though this was probably not the intent of the designers of the first MUDs.
Victories also give the player experience and advancement in game standing.
I can hear some people groaning out there. Must be booooooring. Wrong, wrong, wrong. No game I've ever heard of inspires the emotional highs and lows that a MUD does. This is at least partly due to the fact that it is a long game.