rebuttal vs refutation

rebuttal and refutation both are nouns.

Word	Noun	Adjective	Verb	Adverb
rebuttal	Yes	No	No	No
refutation	Yes	No	No	No

As nouns, refutation is a hypernym of rebuttal; that is, refutation is a word with a broader meaning than rebuttal:

rebuttal: the speech act of refuting by offering a contrary contention or argument
refutation: the speech act of answering an attack on your assertions

Other hypernyms of rebuttal include defence, defense.

rebuttal (noun)	refutation (noun)
the speech act of refuting by offering a contrary contention or argument	the act of determining that something is false
(law) a pleading by the defendant in reply to a plaintiff's surrejoinder	any evidence that helps to establish the falsity of something
	the speech act of answering an attack on your assertions