A tiara is a metal band shaped like half a circle and decorated with jewels which a woman of very high social rank wears on her head at formal social occasions; also used of similar ornaments that girls or women wear on their heads.
tiara in British English
(tɪˈɑːrə)
noun
1.
a woman's semicircular jewelled headdress for formal occasions
2.
a high headdress worn by Persian kings in ancient times
3. Roman Catholic Church
a.
a headdress worn by the pope, consisting of a beehive-shaped diadem surrounded by three coronets
b.
the office or rank of pope
Derived forms
tiaraed (tiˈaraed)
adjective
Word origin
C16: via Latin from Greek, of Oriental origin
tiara in American English
(tiˈɛrə; tiˈærə; tiˈɑrə)
noun
1.
a headdress of the ancient Persians
2.
the pope's high, domed crown consisting of three coronets and an orb and cross
3.
a woman's crownlike headdress of jewels or flowers; coronet