Source : Webster's Revised Unabridged Dictionary (1913)

Opopanax \O*pop"a*nax\, n. [L., fr. Gr. ?; ? vegetable juice +
   ?, ?. a kind of plant: cf. F. opopanax.]
   The inspissated juice of an umbelliferous plant (the
   {Opoponax Chironum}), brought from Turkey and the East Indies
   in loose granules, or sometimes in larger masses, of a
   reddish yellow color, with specks of white. It has a strong
   smell and acrid taste, and was formerly used in medicine as
   an emmenagogue and antispasmodic. --Dunglison.

Source : WordNet®

opopanax
     n : an odorous gum resin formerly used in medicines