The Collaborative International Dictionary of English v.0.48:

Water wheel \Wa"ter wheel`\
   1. 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.
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   2. The paddle wheel of a steam vessel.
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   3. A wheel for raising water; a noria, or the like.
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