\Breast"wheel`\ (br[e^]st" hw[=e]l`), n.
A water wheel, on which the stream of water strikes neither
so high as in the overshot wheel, nor so low as in the
undershot, but generally at about half the height of the
wheel, being kept in contact with it by the breasting. The
water acts on the float boards partly by impulse, partly by
its weight.