Definition
The act of mechanically raising the landing gear from its extended (down and locked) position into the stowed (up and locked) position within the airframe after takeoff, typically commanded by the pilot moving the landing gear selector to the UP position once a positive rate of climb is established and there is no usable runway remaining.
Plain English
Pulling the wheels up into the airplane after takeoff so they're tucked away during flight.
Context Anchor
You encounter this term when operating an airplane with retractable landing gear, especially during the after-takeoff flow and when reading procedures for landing gear operation.
Derivation
Retraction comes from the Latin retrahere, meaning 'to draw back.' The gear is literally drawn back into the airplane.
Why Pilots Care
Improves speed and fuel economy by reducing drag from extended landing gear.
Intuition Check
Do not read “gear” here as general equipment. In this context, it means the landing gear: the wheels and supporting parts the airplane uses on the ground.
Example Sentence 1
After confirming a positive rate of climb on the altimeter, the pilot called for gear retraction and moved the selector to UP.
Example Sentence 2
The airplane's manual specifies the airspeed at which gear retraction should begin.