- Millstone Mill"stone`, n.
One of two circular stones used for grinding grain or other
substance in a mill.
No man shall take the nether or the upper millstone to pledge. --Deut. xxiv. 6. [1913 Webster]
Note: The cellular siliceous rock called buhrstone is usually employed for millstones; also, some kinds of lava, as that Niedermendig, or other firm rock with rough texture. The surface of a millstone has usually a series of radial grooves in which the powdered material collects. [1913 Webster]
The Collaborative International Dictionary of English. 2000.