Glossary
What is a stall in an airplane?
The loss of lift that follows when the wing exceeds its critical angle of attack and the airflow separates from the upper surface. It is an aerodynamic event, not an engine one: the engine goes on running throughout.
Also called Aerodynamic stall
That is the whole entry for now. The longer version, with the mechanics and worked examples, is still to be written. See autorotation for how those read once they exist.