The act of using Facebook while intoxicated. May or may not include confessions of undying love to friends, ex's, or total strangers. Grammar and logic will likely be poor. Similar to a drunk dial.
Chris - "Dude, you left 11 incoherent wall posts on my profile last night. What the fuck?"
Spencer - "What? No, I didn't! Oh, wait...yeah, I was shitfacedbooking."
Combinations of curse words are typically used for insults when angrier than usual. This one, for unknown reasons, sounds better than most others and continues to be used by many in random explosions of anger.