Glassy \Glass"y\, a. 1. Made of glass; vitreous; as, a glassy substance. --Bacon. 2. Resembling glass in its properties, as in smoothness, brittleness, or transparency; as, a glassy stream; a glassy surface; the glassy deep. 3. Dull; wanting life or fire; lackluster; -- said of the eyes. ``In his glassy eye.'' --Byron. {Glassy feldspar} (Min.), a variety of orthoclase; sanidine.