Translated from Chinese's 不三不四，which literally means "not three not four", and metephorically means you're talking non-sense or that this topic of conversation is not based on truth.
Bob: What is he talking about, mountain people mountain sea?
Vincent: Iono man, he's just being not three not four.
Jessica: Hey have you heard about bob's new boyfriend?
Tiffany: Oh stop talking about that not three not four stuff!