Source : Webster's Revised Unabridged Dictionary (1913)

Ammoniac \Am*mo"ni*ac\(or Gum ammoniac \Gum` am*mo"ni*ac\, n.
   [L. Ammoniacum, Gr. ? a resinous gum, said to distill from a
   tree near the temple of Jupiter Ammon; cf. F. ammoniac. See
   {Ammonite}.] (Med.)
   The concrete juice (gum resin) of an umbelliferous plant, the
   {Dorema ammoniacum}. It is brought chiefly from Persia in the
   form of yellowish tears, which occur singly, or are
   aggregated into masses. It has a peculiar smell, and a
   nauseous, sweet taste, followed by a bitter one. It is
   inflammable, partially soluble in water and in spirit of
   wine, and is used in medicine as an expectorant and
   resolvent, and for the formation of certain plasters.

Source : WordNet®

gum ammoniac
     n : the aromatic gum of the ammoniac plant [syn: {ammoniac}]