What does "leaven" mean?

Leaven: 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.

Additional senses

  1. 2.1. To make light by the action of leaven; to cause to ferment. A little leaven leaveneth the whole lump. 1 Cor. v.
  2. 3.2. To imbue; to infect; to vitiate. With these and the like deceivable doctrines, he leavens also his prayer. Milton.

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