antiaircraft vs defensive

antiaircraft and defensive both are nouns.

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

antiaircraft (noun)	defensive (noun)
artillery designed to shoot upward at airplanes	an attitude of defensiveness

antiaircraft (adjective)	defensive (adjective)
designed for defense from a surface position against air attack	intended or appropriate for defending against or deterring aggression or attack
	attempting to justify or defend in speech or writing