Dictionary.net

A metallic element, atomic number 49, atomic weight 114.82, symbol In. It is named from its blue line in the spectrum. (From Dorland, 28th ed)

in'di-um, n. a soft malleable silver-white metallic element.

A rare metallic element, discovered through its spectrum; a blue line. Atomic weight, 115. Symbol, In. [Gr.]

A soft grey metal, discovered by two indigo lines which it shows under spectrum analysis.