A kind of cap worn by the clergy. In the eighteenth century it was transformed from the soft, functional headwear seen in Renaissance paintings into a stiff, ornamental thing characterized by three vertical ridges and topped with a pompom. English custom retained a softer form, but developed four sharp corners; the English square the cap is now often called a "Canterbury cap." (The academic "mortarboard" is a further development of the same type of cap.)
Since 17c., a square cap with three or four upright projections, radiating from the center crown . Worn by Roman Catholic clergy. Developed, since 13c., out of a cap formed like the modern beret. Also BERRETTA, BIRRETTA, BIRETUM, BARRET-CAP, BARETTE, BERET.
The biretta is a square cap with three or four ridges or peaks, sometimes surmounted by a tuft, traditionally worn by Roman Catholic clergy, as well as by some clergy of the Anglican Churches. It is also the term used for a similar cap worn by those holding doctoral degrees from some universities, and is occasionally used for caps worn by advocates in law courts, for instance the Advocates in the Channel Islands and Malta.