■ conjunction formal
1》 with the intention of preventing.
2》 because of the possibility of.
Origin
OE thȳ ls the 'whereby less that', later the læste .
Usage
Lest remains one of the very few contexts in English where the subjunctive mood is, strictly speaking, required. Thus the standard use is she was worrying ~ he be attacked (not ~ he was attacked ). See also subjunctive .