The Collaborative International Dictionary
overshot wheel
Water wheel \Wa"ter wheel`\
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.