Source : Webster's Revised Unabridged Dictionary (1913)

Cottonweed \Cot"ton*weed`\ (-w[=e]d`), n. (Bot.)
   See {Cudweed}.

Source : WordNet®

cottonweed
     n 1: American everlasting having foliage with soft wooly hairs
          and corymbose heads with pearly white bracts [syn: {pearly
          everlasting}, {Anaphalis margaritacea}]
     2: any of various plants of the genus Froelichia found in sandy
        soils and on rocky slopes in warmer regions of America;
        grown for their spikes of woolly white flowers