n. - One who, or that which, propels.
n. - A contrivance for propelling a steam vessel, usually consisting of a screw placed in the stern under water, and made to revolve by an engine; a propeller wheel.
n. - A steamboat thus propelled; a screw steamer.
- A propeller screw placed in front of the supporting planes of an aeroplane instead of behind them, so that it exerts a pull instead of a push. Hence, Tractor monoplane, Tractor biplane, etc.