propeller science definition

A device consisting of a set of two or more twisted, airfoil-shaped blades mounted around a shaft and spun to provide propulsion of a vehicle through water or air, or to cause fluid flow, as in a pump. The lift  generated by the spinning blades provides the force that propels the vehicle or the fluid—the lift does not have to result in an actual upward force; its direction is simply parallel to the rotating shaft.