Definition of: indigo

(in′də·gō) noun
1. A blue coloring substance, C_l6H₁₀N₂O₂, obtained by the decomposition of indican, contained in the indigo plant and now synthetically produced from various aromatic hydrocarbons. Mixed with oil, it forms a paint of great body, but one easily decomposed by impure air.
2. A deep violet blue: often used adjectivally.
3. The indigo plant. [<Sp. <L indicum <Gk. Indikon (pharmakon) Indian (dye), neut. of Indikos Indian]