worm gear

WordReference Random House Unabridged Dictionary of American English © 2026

worm′ gear′, 

1. Mechanical Engineering a mechanism consisting of a worm engaging with and driving a worm wheel, the two axes usually being at right angles, used where a relatively low speed and a relatively large amplification of power are desired.
2. Mechanical Engineering Also called worm wheel. a gear wheel driven by a worm.
Also, worm′gear′. 
• 1875–80

Collins Concise English Dictionary © HarperCollins Publishers::

worm gear, wormgear / ˈwɜːmˌɡɪə/ noun

1. a device consisting of a threaded shaft (worm) that mates with a gearwheel (worm wheel) so that rotary motion can be transferred between two shafts at right angles to each other
2. Also called: worm wheel a gearwheel driven by a threaded shaft or worm