orchil

noun

• 1 [mass noun] a red or violet dye obtained from certain lichens, used as a source of litmus, orcinol, and other pigments.

• 2a lichen with flattened fronds from which orchil is produced.

  • Roccella (order Graphidiales) and other genera: several species, including the Mediterranean R. tinctoria, used for dyeing, and the Madagascan R. montagnei, used for litmus