Definition from Wiktionary, the free dictionary
biretta (plural birettas)
- 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.
1918, W. B. Maxwell, chapter 10, The Mirror and the Lamp:
- 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.