leaven Meaning, Definition & Usage

  1. noun a substance used to produce fermentation in dough or a liquid
    leavening.
  2. noun an influence that works subtly to lighten or modify something
    leavening.
    • his sermons benefited from a leavening of humor
  3. verb cause to puff up with a leaven
    prove; raise.
    • unleavened bread

WordNet

Leav"en noun
Etymology
OE. levain, levein, F. levain, L. levamen alleviation, mitigation; but taken in the sense of, a raising, that which raises, fr. levare to raise. See Lever, n.
Definitions
  1. Any substance that produces, or is designed to produce, fermentation, as in dough or liquids; esp., a portion of fermenting dough, which, mixed with a larger quantity of dough, produces a general change in the mass, and renders it light; yeast; barm.
  2. Anything which makes a general assimilating (especially a corrupting) change in the mass.
    Beware of the leaven of the Pharisees, which is hypocrisy. Luke xii. 1.
Leav"en transitive verb
Wordforms
imperfect & past participle Leavened ; present participle & verbal noun Leavening
Definitions
  1. To make light by the action of leaven; to cause to ferment.
    A little leaven leaveneth the whole lump. 1 Cor. v. 6.
  2. To imbue; to infect; to vitiate.
    With these and the like deceivable doctrines, he leavens also his prayer. Milton.

Webster 1913