cool down vs ice

cool down is not a noun while ice is a noun.

Word	Noun	Adjective	Verb	Adverb
cool down	No	No	Yes	No
ice	Yes	No	Yes	No

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

Other hyponyms of cool down include quench, refrigerate.

cool down (noun)	ice (noun)
	a rink with a floor of ice for ice hockey or ice skating
	an amphetamine derivative (trade name Methedrine) used in the form of a crystalline hydrochloride; used as a stimulant to the nervous system and as an appetite suppressant
	a frozen dessert with fruit flavoring (especially one containing no milk)
	a flavored sugar topping used to coat and decorate cakes
	the frozen part of a body of water
	diamonds
	water frozen in the solid state