1.nounThe wheels, tyres, brakes, shock absorbers etc of an aircraft; its undercarriage.
"Modern landing gear usually has a tricycle configuration."
2.nounAny of the assemblies which support an aircraft when it is on the ground.
"Large modern commercial aircraft have a nose landing gear and two main landing gears."
3.noun(trucking) the bipod stand found near the front end underneath a truck trailer, used to keep the trailer level when not attached to a tractor truck.