This phrase literally means “chicken and duck talking to each other” and is most commonly used in Cantonese. It describes when two people trying to have a discussion are talking past each other because their brains work too differently. If the communication is only in one direction, then it’s 对牛弹琴 (playing instrumental music to a cow), which implies the listening party is not sophisticated enough to understand what is being communicated. Sometimes used in an insulting fashion.