Source : Webster's Revised Unabridged Dictionary (1913)

Tiara \Ti*a"ra\, n. [L., from Gr. ?, ?; of Persian origin.]
   1. 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.

   2. 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.

Source : WordNet®

tiara
     n : a crown-like jewelled headdress worn by women on formal
         occasions