biretta noun1 •A square cap, originally with four ridges across the top, surmounted by a tuft, worn by Roman Catholic clergy (and by some in the Anglican Church). A three-sided biretta is worn by Roman Catholic clergy for liturgical celebrations.To right and left, embedded in their stalls, the other canons sit reverently engrossed, birettas hung on the walls behind; […] — 1964 formsbirettas
