Dry是“干的”，run是“运行”。Dry run是什么意思？请看对话：

    A: I suggest you practice with a dry run.

    B: What’s that?

    A: Organize a dress rehearsal within two weeks of the wedding to ensure that everything goes smoothly.

    Note: This term means “test, rehearsal.” Some people say the idiom came from “dry assembly,” the way a carpenter will put all the pieces of a work together first without glue (“dry”) to test their fit. Others suggest that it came from the Prohibition when moonshine runners would run the route without carrying any alcohol to get to know the route better, and improve their speed for the actual run (hence a “dry” run).