psychedelic

Short definition from Wiktionary

Adjective

1. 1
   Of, containing, generating, or reminiscent of drug-induced hallucinations, distortions of perception, altered awareness, etc.
2. 2
   Having bright colours, abstract shapes, etc. reminiscent of drug-induced hallucinations or distortions of perception.

Noun

1. 1
   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.

Interjection

1. 1
   Awesome, cool, groovy.