A person who impedes the flow of traffic by staying in the left lane. This person is either driving slower than everybody on the road, driving the same speed as the person to their right, or simply driving 1 mph faster than the person to their right. In all cases, they are ignoring the responsibility that comes with driving in the "hammer lane".
Driver drives in left left despite seeing the long line of cars behind them but refuses to move over to the slow lane because it isn't safe to change lanes while talking on the cellphone. This driver is a Left Lane Loser.