[1] : The Collaborative International Dictionary of English v.0.48

woad \woad\, n. oe. wod, as. w=ad; 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      it is now superseded by indigo, but is somewhat used with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
see also:
wad wade isatis tinctoria cruciferae brassicaceae isatin 
isatis tinctoria wild woad reseda luteola weld woad mill 

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