Webster's Revised Unabridged Dictionary · 1913

Woad

Woad , noun

[Old English wod, Anglo-Saxon wād; akin to Dutch weede, German waid, Old High German weit, Danish vaid, veid, Swedish veide, Latin vitrum.]

1.
(Botany) 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.
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 It is now superseded by indigo, but is somewhat used with indigo as a ferment in dyeing.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
Collocations (2)
Wild woad (Botany) , the weld (Reseda luteola). See Weld.
Woad mill , a mill grinding and preparing woad.