What does the term "stall" refer to in aviation?

The term "stall" in aviation specifically refers to a condition where an aircraft experiences a loss of lift due to an excessive angle of attack. When the angle of attack, which is the angle between the wing's chord line and the oncoming airflow, exceeds a critical limit, airflow over the wings becomes turbulent and separates from the wing's surface. This separation leads to a significant reduction in lift, causing the aircraft to stall.

Stalls can occur at any airspeed or altitude and are not restricted to low-speed scenarios; pilots need to be aware of the aircraft's limitations concerning angles of attack to avoid this condition. Recovery from a stall typically involves decreasing the angle of attack to restore smooth airflow over the wings and regain lift.

In contrast, the other terms mentioned, such as engine malfunction or sudden altitude drops, relate to different flight emergencies and do not define what a stall is in the context of aerodynamics and flight behavior.