worm wheel

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The toothed wheel of a worm gear.

Century Dictionary and Cyclopedia

1. n. A wheel which gears with an endless or tangent screw or worm, receiving or imparting motion. By this means a powerful effect with a diminished rate of motion is communicated from one revolving shaft to another. See tangent screw (under tangent), endless screw (under endless, with cut); also cuts under Hindley's screw (at screw) and under steam-engine.

GNU Webster's 1913

1. n. a cogwheel having teeth formed to fit into the spiral spaces of a screw called a worm, so that the wheel may be turned by, or may turn, the worm; -- called also worm gear, and sometimes tangent wheel. See Illust. of Worm gearing, above.

WordNet 3.0

1. n. gear with the thread of a worm