Plain English Meaning
Pulling the wheels up into the airplane after takeoff so the airplane is smoother through the air and can fly faster and climb better.
Full Definition
The act of mechanically folding or drawing the landing gear up into the airframe after takeoff to reduce aerodynamic drag and improve climb and cruise performance.
Context Anchor
Seen in aircraft control and performance discussions, especially after takeoff in airplanes with retractable landing gear.
Derivation
Retraction comes from the Latin retrahere, meaning 'to draw back.' In aviation, it describes the gear being drawn back up into the wings or fuselage once the airplane is safely .