rebuff vs defend

rebuff is a noun but defend is not a noun.

Word	Noun	Adjective	Verb	Adverb
rebuff	Yes	No	Yes	No
defend	No	No	Yes	No

As verbs, defend is a hypernym of rebuff; that is, defend is a word with a broader meaning than rebuff:

Other hypernyms of rebuff include fight, fight back, fight down, oppose.

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

rebuff (verb)	defend (verb)
reject outright and bluntly	argue or speak in defense of
force or drive back	state or assert
	be on the defensive; act against an attack
	protect against a challenge or attack
	protect or fight for as a champion
	fight against or resist strongly
	be the defense counsel for someone in a trial