The definition of psychedelic is something related to drugs that cause hallucinations or altered consciousness, or the sounds and sites associated with these drugs.(adjective)
See psychedelic in Webster's New World College Dictionary
Origin: < psyche + Gr dēloun, to make manifest
See psychedelic in American Heritage Dictionary 4
Origin: + Greek dēloun, to make visible (from dēlos, clear, visible; see dyeu- in Indo-European roots)
Origin: + -ic.
Learn more about psychedelic