[MUD] Abbrev. for "Away From Keyboard". Used to notify
others that you will be momentarily unavailable online.
eg. "Let's not go kill that frost giant yet, I need to go AFK to
make a phone call". Often MUDs will have a command to politely
inform others of your absence when they try to talk with you. The
term is not restricted to MUDs, however, and has become common in
many chat situations, from IRC to Unix talk.