lest

lest的解释
conj. 惟恐,以免
prep. 唯恐,以免
lest的例句
They spoke in whispers lest they should be heard.
他们低声说话，唯恐被别人听见。

We talked in a low voice lest we should wake the baby up.
我们小声说话以免吵醒婴儿。