{ Am*mo"ni*ac (&?;), Am`mo*ni"a*cal (&?;), } a. Of or pertaining to ammonia, or possessing its properties; as, an ammoniac salt; ammoniacal gas.

Ammoniacal engine, an engine in which the vapor of ammonia is used as the motive force. -- Sal ammoniac [L. sal ammoniacus], the salt usually called chloride of ammonium, and formerly muriate of ammonia.

Am*mo"ni*ac (&?;) (or 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.