This is more of a specific sort of word, but I think it's a suitable one none the less. It's from The Great Gatsby.
The uncontrollable and immediate repetition of what someone else has said.
As this isn't a word you would use in daily conversation, I am including yet another word from The Great Gatsby.
Chaotic or riotous
Sentence example: The end of Harry Potter was marked by the tumultuous Battle of Hogwarts.