Plain English Meaning

It's two problems in sequence. First the wings stop flying because they're tilted into the air too steeply. Then, if the airplane is also yawing or skidding when that happens, it can roll over and start corkscrewing toward the ground. Fix the first problem and the second one can't happen.

Full Definition

A linked pair of aerodynamic events in which the wing first exceeds its critical angle of attack and loses lift (the stall), and then, if one wing is more stalled than the other and yaw is present, the airplane departs into an autorotative descent with the wings held at high angle of attack (the ). The spin cannot occur without the stall; the stall must come first.