Plain English Meaning
A wing shape built to keep air flowing over it in smooth, even sheets for as long as possible. Less turbulence over the wing means less drag, which means more speed and efficiency for the same engine power.
Full Definition
A wing cross-section designed to maintain smooth, layered airflow over a large portion of its surface, reducing drag. It typically has a very thin profile, a sharp leading edge, and its maximum thickness located farther back than on a conventional airfoil, which delays the point at which the airflow becomes turbulent.
Context Anchor
Seen in airfoil design, wing shape, and discussions, especially when comparing different wing sections.