Meaning of “psychedelic” - Learner’s Dictionary

psychedelic

adjective uk us /ˌsaɪkəˈdelɪk/
DRUG

Psychedelic drugs make you see things that are not really there.

COLOUR

Psychedelic colours or patterns are very strong, bright, and strange.

(Definition of “psychedelic” from the Cambridge Learner’s Dictionary © Cambridge University Press)