A form of headdress worn by the ancient Persians. According to Xenophon, the royal tiara was encircled with a diadem, and was high and erect, while those of the people were flexible, or had rims turned over.

The pope’s triple crown. It was at first a round, high cap, but was afterward encompassed with a crown, subsequently with a second, and finally with a third. Fig.: The papal dignity.