all at once 1. simultaneously; all at the same time 同时 Don't answer all at once. One at a time, please. 请不要一下子都回答，一次回答一个就行。 The entire group spoke all at once. 整个小组一下子都开始说话了。 We can't get inside all at once, so please wait your turn. 我们不能一下都进去，请耐心等待依次进入。 2. Suddenly and without warning. 毫无预兆地，突然 All at once, Henry began feeling sick. 亨利突然就病了。 All at once the sky darkened. 天突然黑了。