any of several plants (genus Arctium) of the composite family, with large basal leaves and purple-flowered heads covered with hooked prickles
Origin:
bur + dock
See burdock in American Heritage Dictionary 4
noun
Any of several weedy, chiefly biennial plants of the genus Arctium in the composite family, having pink or purplish flower heads surrounded by prickly bracts and forming a bur in fruit.