used to show that someone is afraid or worried that a particular thing might happen
唯恐，生怕:
worried / concerned / anxious etc lest …
He paused, afraid lest he say too much.
他停顿下来，唯恐说得太多。
She was worried lest he should tell someone what had happened.
她担心他会把所发生的事情说出去。
I was afraid to open the door lest he should follow me…
我不敢开门，唯恐他还跟着我。
The president has gone along with the hardliners lest they be tempted to oust him…
总统同意了强硬派的意见，以免他们产生赶他下台的念头。
And, lest we forget, Einstein wrote his most influential papers while working as a clerk.
大家不要忘记，爱因斯坦最有影响力的论文还是当文员的时候写的。