NPC
From BatWiki
NPC stands for Non-player character, ie. a monster.
You should note that the term monster is widely used by players when really meaning a NPC. As BatMUD has a race called monster, they are separated in BatWiki for practical reasons.
As a trivial side note, there is also an NPC with the short description 'monster' in Darkwood.
See list of NPCs.