Word meaning to repeat what another person is saying as a form of mockery?
For example, when a kid repeats what his/her mother is saying because he/she is angry.
I think 'parroting' is perfect for that. It means 'mimic' but also that the person speaking has not thought about the words they are saying.
They might be mimicking, mocking or parroting the person, more likely mimicking.
mimic
verb
imitate (someone or their actions or words), especially in order to entertain or ridicule.
https://en.oxforddictionaries.com/definition/mimic