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

The term "stall" in aviation specifically refers to a loss of lift that occurs when the aircraft exceeds its critical angle of attack. At this angle, the airflow over the wings begins to separate, significantly diminishing the lift generated by the wings. This condition can lead to a decline in altitude if not recovered properly, as the aircraft is no longer able to maintain level flight. Understanding this phenomenon is crucial for pilots, as it highlights the importance of managing angle of attack during flight to ensure safety and control.

The other options do not accurately describe a stall. For instance, a sudden engine failure represents an entirely different in-flight emergency, and while a decrease in aircraft speed can be a factor leading to a stall, it is not the definition of a stall itself. Malfunctions in flight control systems can impact the aircraft's ability to maneuver, but they also do not define what a stall is. Thus, the correct answer centers on the critical angle of attack and its relation to lift.