A hallucinogen is a substance that produces hallucinations. Dictionary.com gives that definition, adds a scientific sense naming mescaline, LSD and psilocybin as examples, and says the word was first recorded in 1950–55, from hallucination plus -gen (Dictionary.com).
It is the older, more clinical of the three words used for these drugs. “Psychedelic”, coined by Humphry Osmond and dated to 1956 or 1957, stresses the mind being revealed (Dictionary.com). “Entheogen”, coined in 1979, was introduced as an alternative to both psychedelic and hallucinogen to stress transcendence over “mere hallucination” (Seale-Feldman, 2026).
The label can mislead. Many people on classic psychedelics report changed perception, colour and meaning more than true hallucinations, meaning things seen that are not there. Researchers also use “hallucinogen” for a wider group of drugs that act in different ways. When you read a study or a law, the word an author chooses says something about the frame: medical, perceptual or religious.
Sources
- Dictionary.com: hallucinogen
- Dictionary.com: psychedelic
- Seale-Feldman, 2026, Culture, Medicine and Psychiatry
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