antiaircraft gun vs antiaircraft

antiaircraft gun and antiaircraft both are nouns.

Word	Noun	Adjective	Verb	Adverb
antiaircraft gun	Yes	No	No	No
antiaircraft	Yes	Yes	No	No

As nouns, antiaircraft gun and antiaircraft are synonyms defined as:

antiaircraft gun and antiaircraft: artillery designed to shoot upward at airplanes

Other synonyms of antiaircraft gun include ack-ack, ack-ack gun, flack, flak, pom-pom.

antiaircraft gun (noun)	antiaircraft (noun)
artillery designed to shoot upward at airplanes	artillery designed to shoot upward at airplanes

antiaircraft gun (adjective)	antiaircraft (adjective)
	designed for defense from a surface position against air attack