—n. 1. a blue dye obtained from various plants, esp. of the genus Indigofera, or manufactured synthetically.
2. See indigo blue (def. 2).
3. any of numerous hairy plants belonging to the genus Indigofera, of the legume family, having pinnate leaves and clusters of usually red or purple flowers.
4. a color ranging from a deep violet blue to a dark, grayish blue.
—adj. Also calledindigo-blue,indigotic. of the color indigo.