2. (Science: machinery) The parts by which motion imparted to one portion of an engine or machine is transmitted to another, considered collectively; as, the valve gearing of locomotive engine; belt gearing; especially, a train of wheels for transmitting and varying motion in machinery. Frictional gearing. See frictional. Gearing chain, an endless chain transmitted motion from one sprocket wheel to another. Spur gearing, gearing in which the teeth or cogs are ranged round either the concave or the convex surface (properly the latter) of a cylindrical wheel; for transmitting motion between parallel shafts, etc.