gear

/gɪr/ n (MACHINE PART)

Definition

› (in a machine) a wheel having pointed parts around the edge that come together with similar parts of other wheels to control how much power from an engine goes to the moving parts of a machine › In a vehicle, a gear is any of several limited ranges of power that are used for different speeds: [U] Use second gear going up a steep hill.

(Definition of gear n (MACHINE PART) from the Cambridge Academic Content Dictionary © Cambridge University Press)