Plain English Meaning
The switch in the cockpit the pilot uses to put the wheels down or pull them up.
Full Definition
A cockpit control used by the pilot to command the landing gear to extend or retract. The switch is typically shaped like a small wheel and is moved to a DOWN position to extend the gear or an UP position to retract it, signaling the gear system to operate.
Context Anchor
You encounter this in airplanes with retractable landing gear, especially during before-landing, after-takeoff, and emergency gear procedures.
Why Pilots Care
Correct use ensures the aircraft is in the proper for each and prevents dangerous situations such as gear-up landings.