illegitimate vs illicit

illegitimate is a noun but illicit is not a noun.

Word	Noun	Adjective	Verb	Adverb
illegitimate	Yes	Yes	No	No
illicit	No	Yes	No	No

As adjectives, illegitimate and illicit are synonyms defined as:

Other synonyms of illegitimate include outlaw, outlawed, unlawful.

illegitimate (noun)	illicit (noun)
the illegitimate offspring of unmarried parents

illegitimate (adjective)	illicit (adjective)
of marriages and offspring; not recognized as lawful	contrary to accepted morality (especially sexual morality) or convention
contrary to or forbidden by law	contrary to or forbidden by law