rebuff vs oppose

rebuff is a noun but oppose is not a noun.

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

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

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

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

rebuff (verb)	oppose (verb)
reject outright and bluntly	be resistant to
force or drive back	be against; express opposition to
	set into opposition or rivalry
	fight against or resist strongly
	act against or in opposition to
	contrast with equal weight or force