Cassock. A loose form of cloak or outer coat, particularly a military one, worn by men. Also a long clerical coat, buttoned over the breast and reaching to the feet, and drawn in at the waist by a broad sash. In the Catholic Church its color varies with the dignity of the wearer: priests wear black; bishops, purple; cardinals, scarlet; and the pope, white. If lined with fur it is called a pelisse.