The Collaborative International Dictionary of English v.0.48:

Indican \In"di*can\, n. [See Indigo.]
   [1913 Webster]
   1. (Chem.) A glucoside (C14H17NO6) obtained from woad
      (indigo plant, Isatis Tinctoria) and other plants (see
      indigo), as a yellow or light brown sirup. When purified
      it is obtained as spear-shaped crystals. It has a nauseous
      bitter taste. By the action of acids, enzymes, etc., it
      breaks down into sugar and indigo. It is the source of
      natural indigo. Chemically it is the 3-glucoside of
      indole, H-indol-3-yl-[beta]-D-glucopyranoside.
      [1913 Webster +PJC]

   2. (Physiol. Chem.) An indigo-forming substance, found in
      urine, and other animal fluids, and convertible into red
      and blue indigo (urrhodin and uroglaucin). Chemically, it
      is indoxyl sulphate of potash, C8H6NSO4K, and is derived
      from the indol formed in the alimentary canal. Called also
      uroxanthin.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Indigo \In"di*go\, n.; pl. Indigoes. [F. indigo, Sp. indigo,
   indico, L. indicum indigo, fr. Indicus Indian. See Indian.]
   [1913 Webster]
   1. A kind of deep blue, one of the seven prismatic colors.
      [1913 Webster]

   2. (Chem.) A blue dyestuff obtained from several plants
      belonging to very different genera and orders, such as,
      the woad, Isatis tinctoria (family Cruciferae),
      Indigofera suffroticosa, Indigofera tinctoria (family
      Leguminosae), Indigofera Anil, Nereum tinctorium,
      Polygonum tinctorium Ait. (family Polygonaceae), etc.;
      called also natural indigo. It is a dark blue earthy
      substance, tasteless and odorless, with a copper-violet
      luster when rubbed. Indigo does not exist in the plants as
      such, but is obtained by decomposition of the glycoside
      indican.
      [1913 Webster]

   Note: Commercial indigo contains the essential coloring
         principle indigo blue or indigotine, with several other
         dyes; as, indigo red, indigo brown, etc., and various
         impurities. Indigo is insoluble in ordinary reagents,
         with the exception of strong sulphuric acid.
         [1913 Webster]

   Chinese indigo (Bot.), Isatis indigotica, a kind of woad.


   Wild indigo (Bot.), the American herb Baptisia tinctoria
      which yields a poor quality of indigo, as do several other
      species of the same genus.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pastel \Pas"tel\, n. [F.; cf. It. pastello. Cf. Pastil.]
   1. A crayon made of a paste composed of a color ground with
      gum water. [Sometimes incorrectly written pastil.]
      "Charming heads in pastel." --W. Black.
      [1913 Webster]

   2. (Bot.) A plant affording a blue dye; the woad (Isatis
      tinctoria); also, the dye itself.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Isatis \I"sa*tis\ (?; 277), n. [L., a kind of plant, Gr. ?
   woad.] (Bot.)
   A genus of herbs, some species of which, especially the
   Isatis tinctoria, yield a blue dye similar to indigo; woad.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Woad \Woad\, n. [OE. wod, AS. w[=a]d; akin to D. weede, G. waid,
   OHG. weit, Dan. vaid, veid, Sw. veide, L. vitrum.] [Written
   also wad, and wade.]
   [1913 Webster]
   1. (Bot.) An herbaceous cruciferous plant (Isatis
      tinctoria) of the family Cruciferae (syn.
      Brassicaceae). It was formerly cultivated for the blue
      coloring matter derived from its leaves. See isatin.
      [1913 Webster]

   2. A blue dyestuff, or coloring matter, consisting of the
      powdered and fermented leaves of the Isatis tinctoria.
      It is now superseded by indigo, but is somewhat used with
      indigo as a ferment in dyeing.
      [1913 Webster]

            Their bodies . . . painted with woad in sundry
            figures.                              --Milton.
      [1913 Webster]

   Wild woad (Bot.), the weld (Reseda luteola). See Weld.


   Woad mill, a mill grinding and preparing woad.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Isatis tinctoria
    n 1: European biennial formerly grown for the blue coloring
         matter yielded by its leaves [syn: dyer's woad, Isatis
         tinctoria]