refuse vs turn down

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

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

As verbs, turn down is a hyponym of refuse; that is, turn down is a word with a more specific, narrower meaning than refuse:

Other hyponyms of refuse include disdain, freeze off, pooh-pooh, reject, scorn, spurn, contract out, regret, repudiate, disobey.

As verbs, refuse and turn down are synonyms defined as:

Other synonyms of refuse include decline, pass up, reject.

As verbs, refuse and turn down are synonyms defined as:

Other synonyms of refuse include reject, turn away.

refuse (noun)	turn down (noun)
food that is discarded (as from a kitchen)

refuse (verb)	turn down (verb)
show unwillingness towards	make lower or quieter
not accept as true	take a downward direction
refuse to let have	reject with contempt
refuse entrance or membership	not accept as true
elude, especially in a baffling way	refuse entrance or membership
resist immunologically the introduction of some foreign tissue or organ