it has 2 aspects:
1)any color or sound (as an isolated entity) that is profound and vivid,that has a different appeal to your senses in comparison to what you sense in your everyday life.
2)an entirety (a song for example) that even if it has no psychedelic sounds in it , the whole orchestration,interchanges and flow makes it so different in approach and conception that really opens a new way of thinking and dreaming.
these are the stereotyped definitions of the word psychedelic (you won't find them anywhere cause i am the author of them )
if you are lost and confused in thesejust listen to:
SHPONGLE-ARE YOU SHPONGLED?
and you will get it instantly