c. 1200, contracted from Middle English phrase les te "less that," from Old English phrase þy læs þe "whereby less that," from þy, instrumental case of demonstrative article þæt "that" + læs (see less) + þe "the." The þy was dropped and the remaining two words contracted into leste.
实用例句
1. He gripped his brother's arm lest he be trampled by the mob.
他紧抓着他兄弟的胳膊，怕他让暴民踩着。
来自《权威词典》
2. They decided to retreat lest they would be between two fires.
他们决定撤退,否则就要受两面夹击.
来自《简明英汉词典》
3. Be careful lest you ( should ) fall from the tree.
小心,不要从树上掉下来.
来自《简明英汉词典》
4. Let me put down your telephone number lest I forget it.
让我先记下你的电话号码,以免忘了.
来自《简明英汉词典》
5. Close the window quickly lest the raindrops ( should ) slant in.