an ornament or dress with which the ancient Persians covered their head, and with which the Armenians and the kings of Pontus are represented on medals; these last, because they were descended from the Persians. Latin authors call it indifferently tiara and cedaria. Strabo says the tiara was in the form of a tower; and the scholiast on Aristophanes affirms that it was adorned with peacocks' feathers.

Tiara is also the name of the pope's triple crown. The tiara and keys are the badge of the papal dignity; the tiara of his civil rank, and the keys of his spiritual jurisdiction. As soon as the pope is dead, his arms are represented with the tiara alone, without the keys. The ancient tiara was a round high cap. John XXIII. first encompassed it with a crown. Boniface VIII. added a second crown, and Benedict XII. a third.