Plain English Meaning

The point where the wing is tilted into the oncoming air so steeply that the air can no longer flow smoothly over the top of it. When that happens, the wing stops producing the lift needed to keep the aircraft flying.

Full Definition

The angle of attack at which the airflow over a wing separates from the upper surface to the point that the wing can no longer produce enough lift to support the aircraft. Beyond this angle, lift decreases sharply and the wing is said to be stalled. The stalling angle for a given wing is essentially fixed by its shape and is not changed by airspeed, weight, or aircraft attitude.

Context Anchor

Seen in lift, stall, and angle-of-attack discussions; in flight, it matters whenever the aircraft is slowed, pulled up, or turned sharply.