[ lest ]
See synonyms for lest on Thesaurus.com
  1. 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.

  2. that (used after words expressing fear, danger, etc.): There was danger lest the plan become known.

Idioms about lest

  1. lest we forget. See entry at lest we forget.

Origin of lest

First recorded 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 conjunction)

Words that may be confused with lest

Words Nearby lest

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use lest in a sentence

  • There is always in the background of my mind dread lest help should reach the enemy before we have done with Sedd-el-Bahr.

  • Terror and fascination caught him; he turned away lest she should reach his secret and communicate her own.

    The Wave | Algernon Blackwood
  • He saw them standing at street corners, watchfully staring lest they should miss the form of joy.

    Bella Donna | Robert Hichens
  • This new-found joy I long pursued in secret, afraid lest it should be discovered and despised as a folly.

  • Underneath these were affectionate hearts quaking with fear lest the home-coming be but a sad one after all.

    Ramona | Helen Hunt Jackson

British Dictionary definitions for lest


/ (lɛst) /

conjunction(subordinating; takes should or a subjunctive verb)
  1. so as to prevent any possibility that: he fled the country lest he be captured and imprisoned

  2. (after verbs or phrases expressing fear, worry, anxiety, etc) for fear that; in case: he was alarmed lest she should find out

Origin of 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