n. (pl. -os) 1 a a natural blue dye obtained from the indigo plant. b a synthetic form of this dye. 2 any plant of the genus Indigofera. 3 (in full indigo blue) a colour between blue and violet in the spectrum. indigotic adj.
[ 16th-c. indico (f. Sp.), indigo (f. Port.) f. L indicum f. Gk indikon INDIAN (dye) ]