Meaning: It can be used to insult a listener (or viewer) who is unable or unwilling to appreciate what one is trying to communicate. In this sense it approximates the English expression "casting pearls before swine."
出處：漢．牟融《理惑論》：“公明儀為牛彈清角之操，伏食如故，非牛不聞，不合其耳矣。