stimulant drug vs drug

stimulant drug and drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
stimulant drug	Yes	No	No	No
drug	Yes	No	Yes	No

As nouns, drug is a hypernym of stimulant drug; that is, drug is a word with a broader meaning than stimulant drug:

stimulant drug (noun)	drug (noun)
a drug that temporarily quickens some vital process	a substance that is used as a medicine or narcotic

stimulant drug (verb)	drug (verb)
	administer a drug to
	use recreational drugs