In the Brave New World, when John tells his friends that he ate civilization and became defiled, what does this symbolize?
I suppose the most likely answer here is that this is supposed to symbolize what happened in the Garden of Eden (according to the book of Genesis in the Bible).
In the Bible, Adam and Eve were pure and sinless. But then they ate from the fruit of the tree of the knowledge of good and evil. God had told them not to eat from that. Once they did, they lost their innocence.
I think that is what happened with John. He feels that he has lost his innocence and that he has been exposed to sin. Now he is trying to get rid of that sin by purging himself.
John was brought from the reservation to the new world where he became a celebrity. He was aware of what he should and should not engage in. One of the main things that he had avoided was having sex and engaging in hat type of play. After he has taken himself to the lighthouse so he can be isolated from the rest of the world he is discovered.
New people come to interview John and he reacts badly. He finally ends up giving in to the sins of civilization. He engages in sexual misconduct and feels that he can rinse the sins of the flesh away from him. As a result he later kills himself.