A propeller
blade or a compressor blade is hitting the oncoming airflow at an angle of
attack that is determined by a combination of the rotational speed and the
incoming airflow. When the incoming speed is low the angle of attack will be
high. When the angle of attack gets too high the blade stalls, just like a
small wing. So when the axial flow in a compressor backs up the blades stall
and the whole thing turns to worms. Note that you can relieve this by dumping
some late stage air to atmosphere - hence bleed valves.