a yellow-flowered European plant of the cabbage family. It was formerly widely grown in Britain as a source of blue dye, which was extracted from the leaves after they had been dried, powdered, and fermented.
Isatis tinctoria, family Cruciferae
dye obtained from the woad plant, now superseded by synthetic products.
Old Englishwād, of Germanic origin; related to Dutch wede and German Waid