varoomba
When approaching a traffic light either in car, on a bike or on foot and progress with a sudden surge of energy only to reconsider and apply the brake. The sudden surge of energy, which is then wasted, is varoomba.
After fighting his way through congested rush hour traffic Bob saw an opening in the cars which would allow him through the intersection if only he hurried, but as he accelerated he then saw the light change to yellow, as he was still at a distance and changed his mind (speed+brake=varoomba).