每日習(xí)語：do sth.off the top of one‘s head

do sth.off the top of one's head
    毫無準(zhǔn)備地干什么事情，臨時(shí)應(yīng)付
    例句：
    I'll just have to give the speech off the top of my head. There's no time to write it down.
    　　
    沒有時(shí)間寫講稿，我只好即席發(fā)言。