an asshole driver who forces you to brake or switch lanes by staying in the far left lane (the one designated for faster traffic) and going slower than the appropriate speed for that lane; a real asshole.
friend 1: "dude, i hope we get home soon."
friend 2: "hey!! this asshole is going 10 under in a 55, what's his problem?"
friend 1: "what a left lane cock, you'll have to switch lanes."