fight off vs rebuff

fight off is not a noun while rebuff is a noun.

Word	Noun	Adjective	Verb	Adverb
fight off	No	No	Yes	No
rebuff	Yes	No	Yes	No

As verbs, fight off and rebuff are synonyms defined as:

Other synonyms of fight off include drive back, repel, repulse.

fight off (noun)	rebuff (noun)
	a deliberate discourteous act (usually as an expression of anger or disapproval)
	an instance of driving away or warding off

fight off (verb)	rebuff (verb)
force or drive back	reject outright and bluntly
	force or drive back