water down vs adulterate

water down is not an adjective while adulterate is an adjective.

Word	Noun	Adjective	Verb	Adverb
water down	No	No	Yes	No
adulterate	No	Yes	Yes	No

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

water down: thin by adding water to
adulterate: corrupt, debase, or make impure by adding a foreign or inferior substance; often by replacing valuable ingredients with inferior ones

Other hypernyms of water down include debase, dilute, load, stretch.

water down (adjective)	adulterate (adjective)
	mixed with impurities

water down (verb)	adulterate (verb)
make less strong or intense	corrupt, debase, or make impure by adding a foreign or inferior substance; often by replacing valuable ingredients with inferior ones
thin by adding water to