psychedelic

Concise Oxford English Dictionary © 2008 Oxford University Press:
psychedelic /ˌsʌɪkəˈdɛlɪk/

▶adjective

• 1 relating to or denoting drugs (especially LSD) that produce hallucinations and apparent expansion of consciousness.

• 2 (of music, especially rock) characterized by musical experimentation and drug-related lyrics.

• 3 having an intense, vivid colour or a swirling abstract pattern.

▶noun a psychedelic drug.

– derivatives
psychedelically adverb.

– origin 1950s: formed irregularly from psyche + Gk dēlos ‘clear, manifest’ + -ic.