clotburPronunciation: /ˈklɒtbəː/Definition of clotbur noun a herbaceous plant of the daisy family with burred fruits, native to tropical America but now found all over the world. Genus Xanthium, family Compositae: two or three species chiefly North American a burdock. Origin: mid 16th century: from dialect clote 'burdock' + burrclotbur in other Oxford dictionaries Definition of clotbur in the US English dictionary