• A substance being studied in the treatment of anxiety or depression in patients with advanced cancer. It is taken from the mushroom Psilocybe mexicana. Psilocybin acts on the brain to cause hallucinations (sights, sounds, smells, tastes, or touches that a person believes to be real but are not real).
  NCI Dictionary of Cancer Terms
  U.S. National Cancer Institute, 2021
• The major of two hallucinogenic components of Teonanacatl, the sacred mushroom of Mexico, the other component being psilocin. (From Merck Index, 11th ed)
  NLM Medical Subject Headings
  U.S. National Library of Medicine, 2021
• (psilocybine) A tryptamine alkaloid, isolated from various genera of fungi including the genus Psilocybe, with hallucinogenic, anxiolytic, and psychoactive activities. In vivo, psilocybine is rapidly dephosphorylated into the active compound psilocin, which activates serotonin 2A (5-HT2A) receptors in the central nervous system (CNS), mimicking the effects of serotonin.
  NCI Thesaurus
  U.S. National Cancer Institute, 2021