LEST (4)

Lest, conj. [[OE. leste, fr. AS. ðȳ lǣs ðē the less that, where ðȳ is the instrumental case of the definite article, and ðē is an indeclinable relative particle, that, who, which. See The, Less, a.]] 1. 1. For fear that; that . . . not; in order that . . . not.
Love not sleep, lest thou come to poverty. Prov. xx. 13. Wherefore let him that thinketh he standeth take heed lest he fall. 1 Cor. x. 12. 2. 2. That (without the negative particle); — after certain expressions denoting fear or apprehension.
I feared Lest I might anger thee. Shak.