Gearing,

Gearing, a term applied to the machinery which communicates motion from one part of a machine to another, and may consist of toothed-wheels, endless bands, &c. When the communication is interrupted, it is out of gear; and when restored, in gear. Straight gearing is used when the planes of motion are parallel; bevelled gearing, when the direction is changed. Gearing may also be 'multiplying' or retarding—i.e. increasing or diminishing the original velocity.