Plain English Meaning

The wing stops flying because it has been tilted too steeply into the oncoming air. When that happens the air can no longer flow smoothly over the top of the wing, and the wing loses most of its lift.

Full Definition

To exceed the critical angle of attack so that the smooth airflow over the wing separates and the wing can no longer produce sufficient lift to support the airplane. An aerodynamic stall is caused by angle of attack, not by airspeed alone — a wing can stall at any airspeed, any attitude, and any power setting if the critical angle of attack is exceeded.

Context Anchor

Seen in maneuver training, including chandelles, where the airplane is climbing and slowing near the end of the maneuver.