Definition of impellers:
(n) :
A rotating component of a device that accelerates fluid, increasing its pressure or flowrate.
(n) :
Especially, such a component that drives the fluid radially (outward from a center of rotation) rather than axially. (Impellers are found in devices such as pumps, water jets, washing machines, and agitated tanks.)
(n) :
Something which or someone who impels.