Source : Webster's Revised Unabridged Dictionary (1913)

Richweed \Rich"weed`\, n. (Bot.)
   An herb ({Pilea pumila}) of the Nettle family, having a
   smooth, juicy, pellucid stem; -- called also {clearweed}.

Source : WordNet®

richweed
     n 1: erect perennial strong-scented with serrate pointed leaves
          and a loose panicle of yellowish flowers; the eastern
          United States [syn: {horse balm}, {horseweed}, {stoneroot},
           {stone-root}, {stone root}, {Collinsonia canadensis}]
     2: a plants of the genus Pilea having drooping green flower
        clusters and smooth translucent stems and leaves [syn: {clearweed},
         {dead nettle}, {Pilea pumilla}]