The act of heroically chugging a beer, generally on one knee, while wearing a cape.
Johnny had decided not to party that night, but when he saw his friend champion chug a 40 ounce bud heavy, his morale was immediately restored.
The act of jacking off while blacked out. Typically results in mortifying embarrassment the following morning.
Pat: Mitch, I know I was drunk last night, but were you beating it on the living room couch last night when I walked in?
Mitch: Wish I remembered bro, I have the bad habbit of Blackin' Off when I drink too much.