Medical Definition of indigo
plural in·di·gos or in·di·goes
1a: a blue dye obtained from indigo plants (as Indigofera tinctoria of Africa and India, I. anil of South America, and I. auriculata of Arabia and Egypt)b: the principal coloring matter C16H10N2O2 of natural indigo usually synthesized as a blue powder with a coppery luster—called also indigotin
2: indigo plant
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