psychedelic /sī′kədel″ik/ [coined in 1956 by Humphry Osmond from Gk, psyche + deloun, to reveal] , 1. describing a mental state characterized by altered sensory perception and hallucination accompanied by euphoria or fear, usually caused by the deliberate ingestion of drugs or other substances known to produce this effect. 2. describing any drug or substance that causes this state, such as mescaline or psilocybin.
