in Mechanical Philosophy, a term employed to express a supposed peculiar exertion of the powers of body, by which a moving body changes the motion of another body by hitting or striking it. The plainest case of this action is when a body in motion strikes another body at rest, and puts it in motion by the stroke. The body thus put in motion is said to be impelled by the other; and this method of producing motion is called impulsion, to distinguish it from pression, thrusting, or protrusion.