Webster's Revised Unabridged Dictionary · 1913

(Chemistry) A rare metallic element, of atomic number 49, discovered in certain ores of zinc, by means of its characteristic spectrum of two indigo blue lines; hence, its name. In appearance it resembles zinc, being white or lead gray, soft, malleable and easily fusible, but in its chemical relation it resembles aluminium or gallium (valence +3). Symbol In. Atomic weight, 114.82.