An impeller (or impellar) is a rotor inside a tube or conduit used to increase (or decrease in case of turbines) the pressure and flow of a fluid.
Read more about Impeller: Impellers in Pumps, Impellers in Water Jets, Impellers in Agitated Tanks, Impellers in Washing Machines, Firefighting Rank Badge, Impellers in Gas Turbine (turboprop) Engines