MUD

In computing, interactive multi-player game, played via the Internet or modem connection to one of the participating computers. MUD players typically have to solve puzzles, avoid traps, fight other participants and carry out various tasks to achieve their goals.

The first MUD was called MUD, and was written by British programmers Roy Trubshaw and Richard Bartle to run on a DEC System 10 mainframe at the University of Essex, England, in 1979.