When someone responds to an old status update on Facebook, days or weeks after the date of posting.
Also known as Twitlag.
"John finally responded to my comment about the 2008 elections. The dude has some serious Facelag."
The facial sensation one experiences while drunk; sloshy cheeks, tingly lips, and heavy eyelids are all components of facelag.
Guy 1: Bro, I have the gnarliest facelag right now. I swear if you slapped me with a fish it wouldn't even phase me.
Guy 2: I know homie you killed that 40 mad quick. I guess this is why they call it getting shitfaced.