When you are very Intoxicated and start posting things on a social network that you would NEVERpost if you were sober.
Frank: "What the hell dude"
Jim: "What?'
Frank: "You said you wanted to fuck my wife on facebook last night"
Jim: "Oh fuck, I think I was shitfacebooking last night."
Frank: "You're Fired" (Punches Jim in the face)
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.