psilocybin

noun

psi·​lo·​cy·​bin ˌsī-lə-ˈsī-bən How to pronounce psilocybin (audio)
: a hallucinogenic indole C12H17N2O4P obtained from a fungus (such as Psilocybe mexicana or P. cubensis synonym Stropharia cubensis)

Examples of psilocybin in a Sentence

Recent Examples on the Web
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The participants had significantly lower levels of inflammation following the treatments, compared to baseline, and those changes persisted a month after their final dose of psilocybin. — Will Stone, NPR, 21 Oct. 2026 Unlike conventional antidepressants, which can take weeks to work and require daily dosing, psilocybin has shown the potential to produce rapid and lasting improvements after just a handful of administrations, Nath said. — Meghana Keshavan, STAT, 15 Oct. 2026 One with the world To find out which parts of the brain were doing the work, the team replaced one network’s psilocybin activity with its sober version and checked how badly the classifier degraded. — Jacek Krywko, ArsTechnica, 10 Oct. 2026 The lead author, Roland Griffiths, gave three dozen healthy adults with no history of drug use a large dose of psilocybin. — Claire Hoffman, Rolling Stone, 21 Sep. 2026 See All Example Sentences for psilocybin

Word History

Etymology

New Latin Psilocybe, fungus genus + -in entry 1

First Known Use

1958, in the meaning defined above

Time Traveler
The first known use of psilocybin was in 1958

Browse Nearby Words

psilate
psilocybin
psilomelane
See all Nearby Words

Cite this Entry

“Psilocybin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/psilocybin. Accessed 27 Oct. 2026.

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Kids Definition

psilocybin

noun
psi·​lo·​cy·​bin ˌsī-lə-ˈsī-bən How to pronounce psilocybin (audio)
: a chemical that is obtained from a fungus and causes hallucinations

Medical Definition

psilocybin

noun
psi·​lo·​cy·​bin ˌsī-lə-ˈsī-bən How to pronounce psilocybin (audio)
: a hallucinogenic indole C12H17N2O4P obtained from a basidiomycetous fungus (as Psilocybe mexicana or P. cubensis synonym Stropharia cubensis)

More from Merriam-Webster on psilocybin

Britannica.com: Encyclopedia article about psilocybin

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