/in"dee euhm/ , n. Chem.
a rare metallic element, soft, white, malleable, and easily fusible, found combined in various ore minerals, esp. sphalerite: so called from the two indigo-blue lines in its spectrum. Symbol: In; at. wt.: 114.82; at. no.: 49; sp. gr.: 7.3 at 20°C.
[ 1860-65; ind ( icum ) INDIGO + -ium -IUM ]