M

Mach number:
The Mach number indicates how fast a vehicle is moving in still air, or conversely how fast the air is flowing past a still object compared to the speed of sound. Mach 0.5 means that the flow speed, or the vehicle speed, is half the speed of sound. Mach 3 means it is three times the speed of sound. For M between 0 and 0.3, the flow is called subsonic, for M between 0.3 and 1 transonic, and for M greater than 1 supersonic.

Magnus effect:
When a spinning cylinder or ball moves through fluid, the velocity on the backward-moving surface is higher than on the opposite side, thus producing a lower pressure. The resultant effect is a force normal to the path; upward, sideways, etc., depending on the direction of the spin.