pooh-pooh vs rebuff

pooh-pooh is not a noun while rebuff is a noun.

Word	Noun	Adjective	Verb	Adverb
pooh-pooh	No	No	Yes	No
rebuff	Yes	No	Yes	No

As verbs, rebuff is a hyponym of pooh-pooh; that is, rebuff is a word with a more specific, narrower meaning than pooh-pooh:

Other hyponyms of pooh-pooh include repel, snub.

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

pooh-pooh (verb)	rebuff (verb)
reject with contempt	reject outright and bluntly
express contempt about	force or drive back