propeller

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A device for propelling an aircraft or boat, consisting of a shaft with radiating blades that are placed so as to thrust air or water in a desired direction when spinning.

from The Century Dictionary.

• noun In electricity, in the tangential system of traction, the moving part of the system, corresponding to the rotor of an alternator, which is drawn along by the inductive action of the stator-coils between the track and thus affords motive power for the attached cars.
• noun One who or that which propels; in marine engineering, broadly, any contrivance or appliance, as a sail, paddle, oar, paddle-wheel, screw, etc., used for moving vessels floating upon the surface of water, or under the surface; in a more restricted and more generally accepted sense, any instrument or appliance, and especially a screw, used for marine propulsion and actuated by machinery (usually a steam-engine called a marine engine) carried by the vessel so propelled.
• noun A boat or vessel driven by a propeller.
• noun In fishing, a kind of trolling-hook with artificial bait, fitted with wings or flanges to make it spin in the water; a spinning-bait.
• noun See the qualifying words.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who, or that which, propels.
• noun 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.
• noun A steamboat thus propelled; a screw steamer.
• noun the screw, usually having two or more blades, used in propelling a vessel.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun One who, or that which, propels.
• noun A mechanical device, with shaped blades that turn on a shaft, to push against air or water, especially one used to propel an aircraft or boat.
• noun A steamboat thus propelled; a screw steamer.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a mechanical device that rotates to push against air or water