The act of staying up to all hours of the night chatting away with your long lost friend, pen pal, or sexting buddy on Facebook. You can talk about your favorite TV show, how much weight you've gained/lost, the massive dump you just took, or which girl's picture you hate the most. But best of all, you can stay up all night talking to someone without actually talking to someone!
Betty: What'd you do last night, Sal? You look rough.
Sal: Oh I just had a facebook slumber party with Tina. We were up until three in the morning just laughing our souls out!