WordWeb Online

1. Producing distorted sensory perceptions and feelings or altered states of awareness or sometimes states resembling psychosis
   "psychedelic drugs like psilocybin and mescaline"
    
2. Having the vivid colours and bizarre patterns associated with psychedelic states
   "a psychedelic painting"
    
3. (of a mental state) characterized by intense and distorted perceptions and hallucinations and feelings of euphoria or sometimes despair
   "a psychedelic experience"

See also: agitated, colorful [US], colourful [Brit, Cdn], psychedelia, psychoactive, psychotropic

Encyclopedia: Psychedelic