hallucinogen vs psychedelic drug

hallucinogen and psychedelic drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
hallucinogen	Yes	No	No	No
psychedelic drug	Yes	No	No	No

As nouns, hallucinogen and psychedelic drug are synonyms defined as:

hallucinogen and psychedelic drug: a psychoactive drug that induces hallucinations or altered sensory experiences

Other synonyms of hallucinogen include hallucinogenic drug, psychodelic drug.

hallucinogen (noun)	psychedelic drug (noun)
a psychoactive drug that induces hallucinations or altered sensory experiences	a psychoactive drug that induces hallucinations or altered sensory experiences