Glossary
What is a spin?
A stall in which one wing is more deeply stalled than the other, so the airplane descends in a corkscrew while it rotates. It is a different condition from a spiral dive, where the wings are still flying and the airspeed climbs quickly.
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.