Source : Webster's Revised Unabridged Dictionary (1913)

Cocklebur \Coc"kle*bur`\, n. (Bot.)
   A coarse, composite weed, having a rough or prickly fruit;
   one of several species of the genus {Xanthium}; -- called
   also {clotbur}.

Source : WordNet®

cocklebur
     n 1: any coarse weed of the genus Xanthium having spiny burrs
          [syn: {cockle-bur}, {cockleburr}, {cockle-burr}]
     2: burdock having heart-shaped leaves found in open woodland,
        hedgerows and rough grassland of Europe (except extreme N)
        and Asia Minor; sometimes cultivated for medicinal and
        culinary use [syn: {great burdock}, {greater burdock}, {Arctium
        lappa}]