The Collaborative International Dictionary of English v.0.48:

Coltsfoot \Colts"foot`\, n. (Bot.)
   A perennial herb (Tussilago Farfara), whose leaves and
   rootstock are sometimes employed in medicine.
   [1913 Webster]

   Butterbur coltsfoot (Bot.), a European plant (Petasites
      vulgaris).
      [1913 Webster]