Woad n. [Written also wad, and wade.]
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.
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 It is now superseded by indigo, but is somewhat used with indigo as a ferment in dyeing.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.
n 1: a blue dyestuff obtained from the woad plant
2: any of several herbs of the genus Isatis