illicit vs sexual activity

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

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

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

illicit (adjective)	sexual activity (adjective)
contrary to accepted morality (especially sexual morality) or convention
contrary to or forbidden by law