counterfeit vs imitative

counterfeit is a noun but imitative is not a noun.

Word	Noun	Adjective	Verb	Adverb
counterfeit	Yes	Yes	Yes	No
imitative	No	Yes	No	No

As adjectives, counterfeit and imitative are synonyms defined as:

counterfeit (noun)	imitative (noun)
a copy that is represented as the original

counterfeit (adjective)	imitative (adjective)
not genuine; imitating something superior	marked by or given to imitation
	(of words) formed in imitation of a natural sound
	not genuine; imitating something superior

counterfeit (verb)	imitative (verb)
make a copy of with the intent to deceive