What is the meaning of Psychedelic?

Of, containing, generating, or reminiscent of drug-induced hallucinations, distortions of perception, altered awareness etc.

Having bright colours, abstract shapes, etc. reminiscent of drug-induced hallucinations or distortions of perception.

Any psychoactive substance (such as LSD or psilocybin) which, when consumed, causes perceptual changes (sometimes erratic and uncontrollable), visual hallucination, and altered awareness of the body and mind.

awesome, cool, groovy

Source: wiktionary.org