The Collaborative International Dictionary of English v.0.48:

Margosa \Mar*go"sa\, n. [Pg. amargoso bitter.] (Bot.)
   A large tree of the genus Melia (Melia Azadirachta) found
   in India. Its bark is bitter, and used as a tonic. A valuable
   oil is expressed from its seeds, and a tenacious gum exudes
   from its trunk. The Melia Azedarach is a much more showy
   tree, and is cultivated in the Southern United States, where
   it is known as Pride of India, Pride of China, or bead
   tree. Various parts of the tree are considered anthelmintic.
   [1913 Webster]

         The margosa oil . . . is a most valuable balsam for
         wounds, having a peculiar smell which prevents the
         attacks of flies.                        --Sir S.
                                                  Baker.
   [1913 Webster] Margravate

WordNet (r) 3.0 (2006):

margosa
    n 1: large semi-evergreen tree of the East Indies; trunk exudes
         a tenacious gum; bitter bark used as a tonic; seeds yield
         an aromatic oil; sometimes placed in genus Melia [syn:
         neem, neem tree, nim tree, margosa, arishth,
         Azadirachta indica, Melia Azadirachta]