A fork of Rural Dictionary
When you leave your computer logged into to some session (email, chat room, etc) and step away from your computer without locking your screen, someone who notices this is allowed to sneak up and email or message anyone pretending to be you. Typically they will create a long, silly message (possibly admitting how you have always been a homosexual or something of that nature) and at the end put something about how you have "baggy pants."
Joe walked out of the computer lab still logged in to his email and I baggy pantsed the shit out of him on his fraternity list. Noob.