n. 磨石, 磨难, 重担

Millstone \Mill"stone`\, n.
One of two circular stones used for grinding grain or other
substance in a mill[1].

No man shall take the nether or the upper millstone to
pledge. --Deut. xxiv.
6.

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.

{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.)