A rotation of the forearm that moves the palm from an anterior-facing position to a posterior-facing position, or palm facing down. This is not medial rotation as this must be performed when the arm is half flexed.
An inward rotation of the hands toward the body's centerline when standing in a palms-facing-forward position. (The term pronation was inaccurately used for many years to describe the rotation of both hands through the impact area. In fact, one hand, the right, was pronating while the left was supinating. Obviously, it is impossible to pronate both hands through the shot.)