What does Shakespeare mean by the word lest?

In Shakespeare's time, the word "lest" was used in a similar sense to how we use it today. It is used to express a negative purpose, or to prevent something from happening. For example, in the play "Romeo and Juliet," Shakespeare writes: "Lest in revenge of my injuries, / Thy beauty be their excuse." In this line, Shakespeare is saying that he would rather not have his beauty be used as an excuse for the injuries he has suffered.