One of two circular stones used for grinding grain or
other substance.
1. An apparition; a specter. [Obs.] 2. (Opt.) (a) The several colored and other rays of which light is composed, separated by the refraction of a prism or other means, and observed or studied either as spread out on a screen, by direct vision, by photography, or otherwise. See Illust. of Light, and Spectroscope. (b) A ...
