Run基本的意思就是“跑”，也可以是“过程、时间”。Mill是“工厂”。Run of the mill是什么意思呢？请看对话：

    A: Have you seen “Somewhere Only We Know?”

    B: Yeah. This movie had so much publicity I thought it would be good. But to tell you the truth, it was just run of the mill.

    Note: Like “run of the kiln” and “run of the mine,” the phrase refers to products that come direct from the mill in an ungraded state and may contain some imperfections. The mill in question was a weaving mill and the articles first called “run of the mill” were clothes. The phrase originated from the United States in the 19th century. Now it can refer to all kinds of stuff. In a word, to say something is “run of the mill” means it is “quite ordinary” and “not very good.”