filthy vs sexual activity

filthy is not a noun while sexual activity is a noun.

Word	Noun	Adjective	Verb	Adverb
filthy	No	Yes	No	No
sexual activity	Yes	No	No	No

filthy (noun)	sexual activity (noun)
	activities associated with sexual intercourse

filthy (adjective)	sexual activity (adjective)
disgustingly dirty; filled or smeared with offensive matter
characterized by obscenity
vile; despicable