rebuff vs turn down

rebuff is a noun but turn down is not a noun.

Word	Noun	Adjective	Verb	Adverb
rebuff	Yes	No	Yes	No
turn down	No	No	Yes	No

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

Other hypernyms of rebuff include disdain, freeze off, pooh-pooh, reject, scorn, spurn.

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

rebuff (verb)	turn down (verb)
reject outright and bluntly	make lower or quieter
force or drive back	take a downward direction
	reject with contempt
	not accept as true
	refuse entrance or membership