The Collaborative International Dictionary of English v.0.48:
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. Before it is sent, the pallium
is laid on the tomb of St. Peter, where it remains all
(a) The mantle of a bivalve. See Mantle.
(b) The mantle of a bird.