psychedelic , ca . ( Of the ingl. ) psychedelic, and this of the Gr. ?, alma, d?, obvious, manifest, and the English. (do -CI ,? ´ico). 1. adj. belonger or relating to the manifestation of psychic elements that under normal conditions are hidden, or the intense stimulation of psychic powers. Been psychedelic. 2. adj. said especially of drugs such as marijuana and other hallucinogens: cause of this event or stimulation. 3. adj. Colloq. Rare, extravagant, out of the norm to the.