biretta

plural birettas

1. 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, Jan Morris, Spain, Faber and Faber, published 2008, →ISBN

   1 more example

   It was a joy to snatch some brief respite, and find himself in the rectory drawing–room. Listening here was as pleasant as talking; just to watch was pleasant. The young priests who lived here wore cassocks and birettas; their faces were fine and mild, yet really strong, like the rector's face; and in their intercourse with him and his wife they seemed to be brothers.

   1918, W[illiam] B[abington] Maxwell, chapter X, in The Mirror and the Lamp, Indianapolis, Ind.: The Bobbs-Merrill Company, →OCLC