lest

/lest/📚 9016 91 1四级六级考研
If you do something lest something unpleasant should happen, you do it to try to prevent the unpleasant thing from happening. 以防

conjunction [从属连词]以免,避免;唯恐,担心

I was afraid to open the door lest he should follow me.  我当时害怕打开那个门惟恐他跟踪我。

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