Plain English Meaning
Sturdy bars or beams running from the underside of the wing down to the fuselage that help hold the wing in place and carry the loads it experiences in flight.
Full Definition
External support members that connect the wing to the fuselage on certain airplane designs, transmitting flight and landing loads between the wing and the airframe so the wing structure itself can be lighter.
Context Anchor
Seen during preflight inspection and in discussions of the outer wing surfaces and the airplane’s supporting structure.
Derivation
Strut comes from an old Germanic word meaning to stand stiff or rigid. A strut is a stiff support, which is exactly what these members do for the wing.
Why Pilots Care
They maintain wing rigidity and prevent excessive flexing, directly affecting and flight on braced-wing designs.