on the qui vive
警惕地注意，隨時準備應對可能的危險或意外情況
正式·描述高度警覺
英文釋義
being on high alert or watchful for something
例句
The guards were on the qui vive for any sign of intruders.
典故來源
源自法語短語'qui vive?'（誰在？），哨兵詢問口令時的警惕狀態。