'Millstone girt' definitions:

Definition of 'Millstone girt'

From: GCIDE

Millstone \Mill"stone`\, n. One of two circular stones used for grinding grain or other substance in a mill[1]. [1913 Webster]
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]
Millstone girt (Geol.), a hard and coarse, gritty sandstone, dividing the Carboniferous from the Subcarboniferous strata. See Farewell rock, under Farewell, a., and Chart of Geology.
To see into a millstone or To see through a millstone, to see into or through a difficult matter. (Colloq.) [1913 Webster]