Ob-sĭd'i-an, n.

n. [Lat. Obsidianus lapis, so named, according to Pliny, after an Obsidius, who discovered it in Ethiopia; Fr. obsidiane, obsidienne, Sp. obsidiana, It. ossidiana.] (Min.) A kind of glass produced by volcanoes. It is usually of a black color, and opaque, except in thin splinters. Dana.