n. (Chem.) An alkaline salt of fluorescein, obtained as a brownish red substance, which is used as a dye; -- so called from the peculiar yellowish green fluorescence (resembling that of uranium glass) of its solutions. See Fluorescein. [ 1913 Webster ]
n. (Min.) A mineral consisting chiefly of uranium oxide with some lead, thorium, etc., occurring in black octahedrons, also in masses with a pitchlike luster; pitchblende. [ 1913 Webster ]