cool down vs cool

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

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

As verbs, cool down and cool are synonyms defined as:

Other synonyms of cool down include chill.

As verbs, cool down and cool are synonyms defined as:

Other synonyms of cool down include chill.

As verbs, cool down and cool are synonyms defined as:

Other synonyms of cool down include cool off.

cool down (noun)	cool (noun)
	the quality of being at a refreshingly low temperature
	great coolness and composure under strain

cool down (adjective)	cool (adjective)
	neither warm nor very cold; giving relief from heat
	psychologically cool and unenthusiastic; unfriendly or unresponsive or showing dislike
	inducing the impression of coolness; used especially of greens and blues and violets when referring to color
	marked by calm self-control (especially in trying circumstances); unemotional
	fashionable and attractive at the time; often skilled or socially adept
	being satisfactory or in satisfactory condition
	used of a quantity or amount (especially of money) for emphasis