What does ammoniac or gum ammoniac mean?
The definition of ammoniac and gum ammoniac
Am*mo”ni*ac ([or] Gum` am*mo”ni*ac , n.
Etym: [L. Ammoniacum, Gr. 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.