lest /lɛst/ conjunction2 •(formal, literary) For fear that; that not; in order to prevent something from happening; in case.He won't go outside, lest he be eaten by those ravenous eagles.I brought my notes lest faulty memory lead me astray. •(formal, literary) that (without the negative particle; introduces the reason for an emotion.)There was danger/alarm lest the plan become known.I am afraid lest I revealed too much.
