A plant formerly cultivated in Europe and Great Britain for the blue dye extracted from its leaves [Middle & Old English]. The word "oad" is an form of woad [obsolete]. France and Germany, because their farmers grew woad, strongly rejected the use of indigo from India that produced the same blue color, even though indigo had a coloring potential 30 times more potent than woad. However, England and Holland embraced the use of indigo because woad was not one of their major crops. England was the major exporter of indigo to Europe from India in the 18th & 19th centuries. Most of todays indigo is a synthetic product.