psilocybin

noun

psi·​lo·​cy·​bin ˌsī-lə-ˈsī-bən 

: 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

Eating mushrooms that contain psilocybin can have various effects, ranging from euphoria to hallucinations, according to the agency. —Charna Flam, PEOPLE, 5 Sep. 2025

Psychedelic research mushrooms Research interest in recreational drugs or psychedelics such as LSD, psilocybin, ketamine and MDMA has mushroomed in recent years. —Ken Alltucker, USA Today, 4 Sep. 2025

At about the same time, a psilocybin facilitator will come to begin a ritual using the psychedelic drug. —Eileen Finan, People.com, 31 Aug. 2025

It’s been decriminalized or legalized in a handful of states and cities, with New Mexico recently joining this list, creating a legal pathway for the medical use of psilocybin. —Benjamin Adams, Forbes.com, 19 Aug. 2025

Word History

Etymology

New Latin Psilocybe, fungus genus + -in entry 1

First Known Use

1958, in the meaning defined above

Kids Definition

psilocybin

noun

psi·​lo·​cy·​bin ˌsī-lə-ˈsī-bən 

: a chemical that is obtained from a fungus and causes hallucinations

Medical Definition

psilocybin

noun

psi·​lo·​cy·​bin ˌsī-lə-ˈsī-bən 

: a hallucinogenic indole C₁₂H₁₇N₂O₄P obtained from a basidiomycetous fungus (as Psilocybe mexicana or P. cubensis synonym Stropharia cubensis)