lest [lest]

以下由轻松背单词网站提供

conj.唯恐，以免

in order to prevent any possibility that something will happen

Let me put down your telephone number lest I forget it. 让我先记下你的电话号码，以免忘了。
Be careful lest you fall from that tree. 要当心，以免从树上摔下来。