Source : Webster's Revised Unabridged Dictionary (1913)

Cataplasm \Cat"a*plasm\, n. [L. cataplasma, Gr. ?, fr. ? to
   spread over; kata` down, wholly + ? to form, mold.] (Med.)
   A soft and moist substance applied externally to some part of
   the body; a poultice. --Dunglison.

Source : WordNet®

cataplasm
     n : a medical dressing consisting of a soft heated mass of meal
         or clay that is spread on a cloth and applied to the skin
         to treat inflamed areas or improve circulation etc. [syn:
          {poultice}, {plaster}]