The Collaborative International Dictionary of English v.0.48:

Mud \Mud\ (m[u^]d), n. [Akin to LG. mudde, D. modder, G. moder
   mold, OSw. modd mud, Sw. modder mother, Dan. mudder mud. Cf.
   Mother a scum on liquors.]
   Earth and water mixed so as to be soft and adhesive.
   [1913 Webster]

   Mud bass (Zool.), a fresh-water fish (Acantharchum
      pomotis or Acantharchus pomotis) of the Eastern United
      States. It produces a deep grunting note.

   Mud bath, an immersion of the body, or some part of it, in
      mud charged with medicinal agents, as a remedy for
      disease.

   Mud boat, a large flatboat used in dredging.

   Mud cat. See mud cat in the vocabulary.

   Mud crab (Zool.), any one of several American marine crabs
      of the genus Panopeus.

   Mud dab (Zool.), the winter flounder. See Flounder, and
      Dab.

   Mud dauber (Zool.), a mud wasp; the mud-dauber.

   Mud devil (Zool.), the fellbender.

   Mud drum (Steam Boilers), a drum beneath a boiler, into
      which sediment and mud in the water can settle for
      removal.

   Mud eel (Zool.), a long, slender, aquatic amphibian (Siren
      lacertina), found in the Southern United States. It has
      persistent external gills and only the anterior pair of
      legs. See Siren.

   Mud frog (Zool.), a European frog (Pelobates fuscus).

   Mud hen. (Zool.)
   (a) The American coot (Fulica Americana).
   (b) The clapper rail.

   Mud lark, a person who cleans sewers, or delves in mud.
      [Slang]

   Mud minnow (Zool.), any small American fresh-water fish of
      the genus Umbra, as Umbra limi. The genus is allied to
      the pickerels.

   Mud plug, a plug for stopping the mudhole of a boiler.

   Mud puppy (Zool.), the menobranchus.

   Mud scow, a heavy scow, used in dredging; a mud boat.
      [U.S.]

   Mud turtle, Mud tortoise (Zool.), any one of numerous
      species of fresh-water tortoises of the United States.

   Mud wasp (Zool.), any one of numerous species of
      hymenopterous insects belonging to Pepaeus, and allied
      genera, which construct groups of mud cells, attached,
      side by side, to stones or to the woodwork of buildings,
      etc. The female places an egg in each cell, together with
      spiders or other insects, paralyzed by a sting, to serve
      as food for the larva. Called also mud dauber.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mud bath
    n 1: a bath in warm mud (as for treating rheumatism)