Plain English Meaning

Wings shaped the same on top as on the bottom. Because both sides match, the wing doesn't lift on its own when flying level into the wind — the pilot has to angle it slightly to make lift.

Full Definition

Wings whose airfoil cross-section has identical curvature on the upper and lower surfaces, so the shape above the chord line mirrors the shape below it. A symmetrical airfoil produces zero lift at zero angle of attack and generates lift only when the wing is tilted relative to the oncoming air.

Context Anchor

Seen in airfoil behavior discussions when comparing symmetrical wings with cambered wings and explaining how wing shape affects lift.