acidulous vs acid

acidulous is not a noun while acid is a noun.

Word	Noun	Adjective	Verb	Adverb
acidulous	No	Yes	No	No
acid	Yes	Yes	No	No

As adjectives, acidulous and acid are synonyms defined as:

Other synonyms of acidulous include acidic, acidulent.

acidulous (noun)	acid (noun)
	street name for lysergic acid diethylamide
	any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt

acidulous (adjective)	acid (adjective)
being sour to the taste	having the characteristics of an acid
	being sour to the taste
	harsh or corrosive in tone