3D MUD

From Gekkeiju Online

3D MUD isn't really an official definition but it's the only one really suitable for graphical online RPGs that are based on MUDs.

3D MUDs are basically games based on MUD-systems which use 3D graphics instead of text. Moving to the graphical world, however, makes it impossible to implement some 'features'. Text-based MUDs were always extendable to any direction which naturally isn't possible in 3D MUDs where the player needs to see everything as graphics.

Another difference between MUDs and 3D MUDs is that 3D MUDs need a unique client that doesn't work with other 3D MUDs. This means that 3D MUDs are usually considered MMORPGs. Most 3D MUDs, however, want to point out the real definition as most MMORPGs nowadays are just crappy clones that bring nothing new to the genre.