Noun | 1. | ![]() escape wheel - gear that engages a rocking lever pinion - a gear with a small number of teeth designed to mesh with a larger wheel or rack epicyclic gear, planet gear, planet wheel, planetary gear - an outer gear that revolves about a central sun gear of an epicyclic train rack and pinion - a wheel gear (the pinion) meshes with a toothed rack; converts rotary to reciprocating motion (and vice versa) spur gear, spur wheel - gear wheels that mesh in the same plane sun gear - the central gear in an epicyclic train tooth - one of a number of uniform projections on a gear wheel - a simple machine consisting of a circular frame with spokes (or a solid disc) that can rotate on a shaft or axle (as in vehicles or other machines) worm gear - gear consisting of a shaft with screw thread (the worm) that meshes with a toothed wheel (the worm wheel); changes the direction of the axis of rotary motion worm wheel - gear with the thread of a worm |