When you're on Live Messenger and you tell people you're signing off then you change your status to "Appear Offline"...like so people think you have signed off but you're actually lurking in the msn shadows, waiting to pounce when someone cooler signs in.

When a person, or group of people for that matter, enter a social establishment or gathering, with the intent of getting inebriated without the social and relationshipial backlash of having ones photo's tagged on Facebook.

A mode in which one immediately crouches in the fastest and quietest way possible.