Speedpainting is painting something in a very short amount of time. Speedpaints are typically done in less than 2 hours, often in really short bursts like 20 minutes or even 5 minutes on a piece. It's a good exercise because the time constraint forces you to stop worrying about the little things and focus on the big picture. If you want to give it a shot, I recommend trying to draw/paint something in 3 minutes to complete a few drawings, then giving yourself 5 minutes, then giving yourself 40. You'd be surprised how quickly you can learn new skills/techniques and how much faster your painting can become.