When you are signed into MSN Messenger but appearing offline.
Bob: "Where were you last night? I waited hours for you to come online!"
Terry: "I was there, I guess I must have been onffline, I thought you were quiet!"
Bill: "Hey man can I check my messages on your computer"
Ted: "Sure, but make sure I'm onffline when you log on, my ex is kinda stalking me at the moment"