What does "pallium" mean?

Pallium: (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.