Definition
The angle at which a wing is set back from a line perpendicular to the airplane's longitudinal axis, so that the wingtips are positioned aft of the wing root. Sweep is most often rearward (swept-back) and is used primarily on higher-speed airplanes to delay the onset of compressibility effects, but it also alters stall behavior — a swept wing tends to stall at the wingtips first, which can cause the nose to pitch up as the stall develops.
Plain English
It's how far the wings are angled backward from straight out to the side. Wings that point straight out have no sweep; wings that angle back toward the tail are swept.
Context Anchor
Encountered when reading about swept-wing airplanes and how their stall behavior can differ from straight-wing airplanes.
Derivation
“Sweep” comes from the idea of something curving or moving across a space. In aircraft design, it describes how the wing appears to be swept backward or forward across the airplane’s top view.
Why Pilots Care
Greater wing sweep causes stalls to begin at the tips and move inward, reducing aileron effectiveness and stall warning.
Intuition Check
Wing sweep does not mean anything is brushing or cleaning the wing. Here, “sweep” means the wing’s slanted angle when viewed from above.
Example Sentence 1
The airplane's pronounced wing sweep helps it cruise efficiently at high speeds but gives it a tendency to pitch up at the stall.
Example Sentence 2
Higher wing sweep reduces natural stall buffet felt through the controls.