From Tapestries MUCK
OOC stands for "Out of Character." It signifies that what is being said is not part of a roleplay, and may also allude to events occurring in Real Life.
To say something OOC to a room, type
To make a pose OOC, type
Some parts of the MUCK allow for both In Character (IC), as well as OOC conversation. Others, such as Sodom, restrict OOC conversation to specific areas or disallow it completely. Referring to the rules for the zone you're in will be the guidelines on whether or not you may speak OOC there.