libellous vs libel

libellous is not a noun while libel is a noun.

Word	Noun	Adjective	Verb	Adverb
libellous	No	Yes	No	No
libel	Yes	No	Yes	No

libellous (noun)	libel (noun)
	a false and malicious publication printed for the purpose of defaming a living person
	the written statement of a plaintiff explaining the cause of action (the defamation) and any relief he seeks

libellous (adjective)	libel (adjective)
(used of statements) harmful and often untrue; tending to discredit or malign

libellous (verb)	libel (verb)
	print slanderous statements against