Source : Webster's Revised Unabridged Dictionary (1913)

Pallium \Pal"li*um\, n.; pl. L. {Pallia}(?), E. {Palliums}. [L.
   See {Pall} the garment.]
   1. (Anc. Costume) A large, square, woolen cloak which
      enveloped the whole person, worn by the Greeks and by
      certain Romans. It is the Roman name of a Greek garment.

   2. (R.C.Ch.) A band of white wool, worn on the shoulders,
      with four purple crosses worked on it; a pall.

   Note: The wool is obtained from two lambs brought to the
         basilica of St. Agnes, Rome, and blessed. It is worn by
         the pope, and sent to patriarchs, primates, and
         archbishops, as a sign that they share in the plenitude
         of the episcopal office. Befoer it is sent, the pallium
         is laid on the tomb of St. Peter, where it remains all
         night.

   3. (Zo["o]l.)
      (a) The mantle of a bivalve. See {Mantle}.
      (b) The mantle of a bird.

Source : WordNet®

pallium
     n 1: the layer of unmyelinated neurons (the gray matter) forming
          the cortex of the cerebrum [syn: {cerebral cortex}, {cerebral
          mantle}, {cortex}]
     2: (zoology) a protective layer of epidermis in mollusks or
        brachiopods that secretes a substance forming the shell
        [syn: {mantle}]
     3: (Roman Catholic Church) vestment consisting of a band
        encircling the shoulders with two lappets hanging in front
        and back
     4: cloak or mantle worn by men in ancient Rome
     [also: {pallia} (pl)]