帽子掉下來了? at the drop of a hat Meaning:immediately, without hesitation解釋:立刻;毫不猶豫例句:We’re all packed and can leave at the drop of a hat.(我們都收拾好行李了,隨時可以出發。)◇我們都收拾好行李了,隨時可以出發。(123RF)