The Collaborative International Dictionary of English v.0.48:

Zuchetto \Zu*chet"to\, n. [It. zucchetto.] (R. C. Ch.)
   A skullcap covering the tonsure, worn under the berretta. The
   pope's is white; a cardinal's red; a bishop's purple; a
   priest's black.
   [1913 Webster]