lest

[lest] /lɛst/

conjunction

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

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 confused

least, lest, let's.

Examples from the web for lest

The designer won't discuss her plans in more detail, lest she divulge trade secrets.
Also, be sure to stay off the bikers' lane, lest you get clipped or cursed at by speeding cyclists.
At the same time, a welcoming remark should be serious, lest you suggest that the occasion is not a solemn one.
lest you think my rhetoric too strong, look at what the great recession has wrought.
So put the source after the end of the last sentence, lest it be taken as part of the quote.
But the debt limit increase isn't a desire, it's a necessity, lest the nation default on obligations made under both parties.
lest the queen perspire, it has a layer of tint that's both effective and hardly noticeable.
They were terrified by official letters demanding that the domain be handed over lest the matter be referred to company lawyers.
But that's the kind of story that needs to be kept in check, lest it overwhelm everything else on the show.
During that case the paper admitted it had not sought comment from him prior to publication, lest he seek a gagging order.

British Dictionary definitions for lest

lest

/lɛst/

conjunction (subordinating; takes should or a subjunctive verb)

so as to prevent any possibility that: he fled the country lest he be captured and imprisoned

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

Word Origin

Old English the lǣste, earlier thӯ lǣs the, literally: whereby less that

Word Origin and History for lest

conj.

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.