Source : Webster's Revised Unabridged Dictionary (1913)

Pestilence \Pes"ti*lence\, n. [F. pestilence, L. pestilentia.
   See {Pestilent}.]
   1. Specifically, the disease known as the plague; hence, any
      contagious or infectious epidemic disease that is virulent
      and devastating.

            The pestilence That walketh in darkness. --Ps. xci.
                                                  6.

   2. Fig.: That which is pestilent, noxious, or pernicious to
      the moral character of great numbers.

            I'll pour this pestilence into his ear. --Shak.

   {Pestilence weed} (Bot.), the butterbur coltsfoot ({Petasites
      vulgaris}), so called because formerly considered a remedy
      for the plague. --Dr. Prior.

Butterbur \But"ter*bur`\, n. (Bot.)
   A broad-leaved plant ({Petasites vulgaris}) of the Composite
   family, said to have been used in England for wrapping up
   pats of butter.

Coltsfoot \Colts"foot`\, n. (Bot.)
   A perennial herb ({Tussilago Farfara}), whose leaves and
   rootstock are sometimes employed in medicine.

   {Butterbur coltsfoot} (Bot.), a European plant ({Petasites
      vulgaris}).

Source : WordNet®

Petasites vulgaris
     n : small Eurasian herb having broad leaves and lilac-pink
         rayless flowers; found in moist areas [syn: {butterbur},
         {bog rhubarb}, {Petasites hybridus}]