cataplasm

[Middle English cathaplasma and French cataplasme, both from Latin cataplasma, from Greek kataplasma, from kataplassein, to plaster over : kata-, down, onto, over; see cata- + plassein, to mold, form; see plasma.]

The noun has one meaning:

Meaning #1: 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.
  Synonyms: poultice, plaster