indigo blue

noun

1. indigo(def 4).
2. Also called indigo, indigotin. a dark-blue, water-insoluble, crystalline powder, C16H10N2O2, having a bronzelike luster, the essential coloring principle of which is contained along with other substances in the dye indigo and which can be produced synthetically.

noun, adjective (indigo-blue when prenominal)

1. the full name for indigo (def. 1), indigo (def. 3)