The Collaborative International Dictionary of English v.0.48:

Opobalsam \Op`o*bal"sam\, Opobalsamum \Op`o*bal"sa*mum\, n. [L.
   opobalsamum, Gr. ?; ? vegetable juice + ? balsam.] (Med.)
   The old name of the aromatic resinous juice of the
   Balsamodendron opobalsamum, now commonly called balm of
   Gilead. See under Balm.
   [1913 Webster]