biretta, stiff square hat with three or four rounded ridges, worn by Roman Catholic, some Anglican, and some European Lutheran clergy for both liturgical and nonliturgical functions. A tassel or tuft is often attached.
Biretta
The biretta is a square cap with three or four peaks or horns, sometimes surmounted by a tuft. Traditionally the three-peaked biretta is worn by Christian clergy, especially Roman Catholic clergy, as well as some Lutheran and Anglican clergy. Wikipedia
People also ask
Why does the priest wear a biretta?
Why does the biretta have 3 peaks?
A square cap with three ridges or peaks on its upper surface, worn by clerics of all grades from cardinals downwards.