water wheel

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

• noun A wheel propelled by falling or running water and used to power machinery.
• noun A wheel with buckets attached to its rim for raising water.

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

• Any wheel for propelling machinery or for other purposes, that is made to rotate by the direct action of water; -- called an overshot wheel when the water is applied at the top, an undershot wheel when at the bottom, a breast wheel when at an intermediate point; other forms are called reaction wheel, vortex wheel, turbine wheel, etc.
• The paddle wheel of a steam vessel.
• A wheel for raising water; a noria, or the like.

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

• noun A wheel, propelled by running or falling water, used to power machinery.
• noun A wheel with buckets used to raise water.

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

• noun a wheel that rotates by direct action of water; a simple turbine
• noun a wheel with buckets attached to its rim; raises water from a stream or pond