Source : Webster's Revised Unabridged Dictionary (1913)

Bulbul \Bul"bul\, n. [Per.] (Zo["o]l.)
   The Persian nightingale ({Pycnonotus jocosus}). The name is
   also applied to several other Asiatic singing birds, of the
   family {Timaliid[ae]}. The green bulbuls belong to the
   {Chloropsis} and allied genera. [Written also {buhlbuhl}.]

Source : WordNet®

bulbul
     n : nightingale spoken of in Persian poetry