Source : Webster's Revised Unabridged Dictionary (1913)

Bahai \Ba*hai"\ (b[.a]*h[imac]"), n.; pl. {Bahais} (-h[imac]z).
   A member of the sect of the Babis consisting of the adherents
   of Baha (Mirza Husain Ali, entitled ``Baha 'u 'llah,'' or,
   ``the Splendor of God''), the elder half brother of Mirza
   Yahya of Nur, who succeeded the Bab as the head of the
   Babists. Baha in 1863 declared himself the supreme prophet of
   the sect, and became its recognized head. There are upwards
   of 20,000 Bahais in the United States.

Source : WordNet®

Bahai
     adj : of or relating to Bahaism
     n : a teacher of or believer in Bahaism