| Noun | 1. | genus Xanthium - coarse herbs having small heads of greenish flowers followed by burrs with hooked bristles asterid dicot genus - genus of more or less advanced dicotyledonous herbs and some trees and shrubs aster family, Asteraceae, Compositae, family Asteraceae, family Compositae - plants with heads composed of many florets: aster; daisy; dandelion; goldenrod; marigold; lettuces; ragweed; sunflower; thistle; zinnia cocklebur, cockle-bur, cockleburr, cockle-burr - any coarse weed of the genus Xanthium having spiny burrs |