IC
From t2twiki
IC stands for "in character". It refers to any situation where your character's actions or words are based on his or her personality, values, and background. By default, it must be appropriate to the setting. Driving a car? OOC. Riding your horse through driving rain to the Forsaken Inn? IC.
A significant number of roleplayers populate Arda. They will appreciate you staying IC when associating with them. Others do not roleplay and may give you funny looks if you try to remain in character while talking to them. Clearly, these social waters require some tact to navigate.
