{i} gear by which the speed of machines or cars can be changed while the propelling engine or motor stays constant
A gear by means of which the speed of machinery or of a vehicle may be changed while that of the propelling engine or motor remains constant; called also change-speed gear
[ 'chAnj ] (verb.) 13th century. Middle English, from Old French changier, from Latin cambiare to exchange, probably of Celtic origin; akin to Old Irish camm crooked.