Official Aviation Definition
An aerodynamic stall is a sudden reduction in the lift generated by an airfoil, occurring when the angle of attack increases beyond the critical threshold. Airflow separates from the upper surface of the wing, leading to turbulent wake, buffeting, loss of roll control, and sudden descent.
In Simple Words
When the wings are tilted too steeply into the wind, the smooth airflow breaks away, and the wing suddenly loses its lift.
Real-World Flight Example
Pilots practice stall recovery by promptly reducing the angle of attack with forward control pressure and adding engine power.