What's the meaning of the idiom play along with?

To "play along with" means to pretend to agree or cooperate with someone or something, even if you do not actually agree or believe in it. It can also mean to go along with a plan or idea in order to keep someone happy or to avoid conflict.

To cooperate with someone, especially by pretending to agree with them or to believe what they say, even if you do not really agree or believe it.