am·mo·ni·ac 2 
(ə-mōnē-ăk′)
(ə-mōnē-ăk′)n.
A strong-smelling gum resin from the stems of a plant (Dorema ammoniacum) of western Asia, formerly used in perfumery and in medicine as an expectorant and a stimulant. Also called gum ammoniac.
[Middle English ammoniak, from Latin ammōniacum, from Ammōniacus, of Amen, from Greek Ammōniakos; see AMMONIA.]