Source : Webster's Revised Unabridged Dictionary (1913)

Pinkroot \Pink"root`\, n.
   1. (Med.) The root of {Spigelia Marilandica}, used as a
      powerful vermifuge; also, that of {S. Anthelmia}. See
      definition 2 (below).

   2. (Bot.)
      (a) A perennial North American herb ({Spigelia
          Marilandica}), sometimes cultivated for its showy red
          blossoms. Called also {Carolina pink}, {Maryland
          pinkroot}, and {worm grass}.
      (b) An annual South American and West Indian plant
          ({Spigelia Anthelmia}).

Source : WordNet®

pinkroot
     n : a fungal disease of onions