A mechanism used to control the direction of travel of a steam locomotive.

A system of gearing permitting the driving shaft to be swivelled so as to set the machine in any direction with relation to the power.

(idiomatic) Full throttle; a maximal level of effort. / Used other than figuratively or idiomatically: see fourth, gear.

(aviation, military) A system used to quickly decelerate a landing aircraft, essential for landing on an aircraft carrier (although land-based airfields can also be equipped with arresting gear); the most common system consists of a series of transverse wire ropes designed to snag an aircraft's tailhook, connected to a hydraulic or mechanical energy-absorbing system, but other systems exist (typically only for use in an emergency situation) which use a net to slow down an aircraft.

A gear in a vehicle transmission which, when selected, enables the vehicle to move in the opposite direction, or backwards. / A gear fitted to a machine which allows it to run backwards.

(mechanical engineering) The simplest type of gear, with teeth projecting radially, parallel to its axis.

(rail transport) Equipment for applying sand onto rails, to aid adhesion in slippery conditions.

(aviation) Landing gear mounted in the roots of an aircraft's wings.

(aviation) The primary landing gear of an aircraft, generally located slightly behind the aircraft's center of mass (or slightly ahead of it on a taildragger aircraft) and carrying the majority of the aircraft's weight.

(aviation) Landing gear mounted in the lower part of an aircraft's fuselage, generally between or slightly behind the wings.