\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}.]
1. (Bot.) An herbaceous cruciferous plant ({Isatis
   tinctoria}). It was formerly cultivated for the blue
   coloring matter derived from its leaves.
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   is now superseded by indigo, but is somewhat used with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.
         Their bodies . . . painted with woad in sundry
         figures.                              --Milton.
{Wild woad} (Bot.), the weld ({Reseda luteola}). See {Weld}.
{Woad mill}, a mill grinding and preparing woad.