indigo
in.di.go \'in-di-.go-\ n or indigos or indigoes [It dial., fr. L indicum,
fr. Gk indikon, fr. neut. of indikos pl X Indic, fr. Indos India 1a: a blue
vat dye obtained from plants (as indigo plants) by alteration of the
indican present 1b: the principal coloring matter C16H10N2O2 of nat ural
indigo usu. synthesized as a blue powder with a coppery luster from
synthetic indoxyl 1c: any of several blue vat dyes derived from or closely
related to indigo 2: a variable color averaging a dark grayish blue