Definitions for obsidianəbˈsɪd i ən
Random House Webster's College Dictionary
ob•sid•i•anəbˈsɪd i ən(n.)
a volcanic glass similar in composition to granite, usu. dark but transparent in thin pieces, and having a good conchoidal fracture.
Origin of obsidian:
1790–1800; < L Obsidiānus, printer's error for Obsiānus pertaining to Obsius, the discoverer (according to Pliny) of a similar mineral in Ethiopia; cf. ME obsianus < L; see -an1
acid or granitic glass formed by the rapid cooling of lava without crystallization; usually dark, but transparent in thin pieces
a type of black glass produced by volcanos
a kind of glass produced by volcanoes. It is usually of a black color, and opaque, except in thin splinters
The Nuttall Encyclopedia
a hard, dark-coloured rock of a glassy structure found in lava, which breaks with conchoidal fracture.