for fear that; so that (one) should not (used negatively to introduce a clause expressive of an action or occurrence requiring caution): He kept his notes by his side lest faulty memory lead him astray.
that (used after words expressing fear, danger, etc.): There was danger lest the plan become known.

Origin of lest

before 1000; Middle English leste, contraction of the lesse the, thi les the; late Old English the lǣste, earlier thȳ lǣs the, literally, whereby less that (thȳ instrumental case of the demonstrative and relative pronoun, lǣs less, the relative particle)
Can be confusedleast lest let's
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for lest

Contemporary Examples of lest

Historical Examples of lest

  • Was he worse and were they afraid to tell her, lest she should go to him!

    Weighed and Wanting

    George MacDonald

  • Stand aside, Arnaud, lest you find a bolt through your gizzard.

    The White Company

    Arthur Conan Doyle

  • Yet they took no active measures in that way, lest they might have cause to regret it.

    The Dream

    Emile Zola

  • Nevertheless, we will have it done, lest their bad example should corrupt the other hogs.

    Tanglewood Tales

    Nathaniel Hawthorne

  • But we were afraid to lose sight of the bridge, lest we should get all adrift.

    Ned Myers

    James Fenimore Cooper

British Dictionary definitions for lest


conjunction (subordinating; takes should or a subjunctive verb)

so as to prevent any possibility thathe fled the country lest he be captured and imprisoned
(after verbs or phrases expressing fear, worry, anxiety, etc) for fear that; in casehe was alarmed lest she should find out

Word Origin for lest

Old English the lǣste, earlier thӯ lǣs the, literally: whereby less that
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for lest

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.

Online Etymology Dictionary, © 2010 Douglas Harper