at the drop of a hat

短语

一发出信号就…,立刻,毫不迟疑地

发音

AU

释义与例句

phr.
  1. 1.

    Without any hesitation; instantly.

    习语 非正式

    We're expected to just do it at the drop of a hat.

    If you need help, just call on Mike. He can come at the drop of a hat.

词源

From the customary starting of competitions by making a sweeping downward motion with a cap.

来源：wiktionary