Posing

n. On a MUD, the use of ':' or an equivalent command to announce to other players that one is taking a certain physical action that has no effect on the game (it may, however, serve as a social signal or propaganda device that induces other people to take game actions). For example, if one's character name is Firechild, one might type ': looks delighted at the idea and begins hacking on the nearest terminal' to broadcast a message that says

"Firechild looks delighted at the idea and begins hacking on the nearest terminal".

See RL.