antiaircraft gun vs flack

antiaircraft gun and flack both are nouns.

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

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

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

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

antiaircraft gun (noun)	flack (noun)
artillery designed to shoot upward at airplanes	artillery designed to shoot upward at airplanes
	intense adverse criticism
	a slick spokesperson who can turn any criticism to the advantage of their employer