Plain English Meaning
A part of the aircraft, like the flaps or landing gear, is in its 'tucked-in' position rather than sticking out.
Full Definition
The fully stowed configuration of an aircraft component such as wing flaps, landing gear, or spoilers, in which the component is pulled in or folded away into the airframe rather than extended for use.
Context Anchor
Seen in checklist and after-landing procedures, especially when moving flaps or other controls after the airplane is clear of the runway and stopped.
Derivation
From the Latin 'retrahere,' meaning 'to draw back.' In aviation, a component in the retracted position has been drawn back into the airframe, the opposite of being extended.