define mass define acceleration.
acceleration - (physics) a rate of increase of velocity. natural philosophy, physics-the science of matter and energy and their interactions; his favorite subject was physics.
Mass and Weight. The mass of an object is a fundamental property of the object; a numerical measure of its inertia; a fundamental measure of the amount of matter in the object. Definitions of mass often seem circular because it is such a fundamental quantity that it is hard to define in terms of something else.