Толковый словарь английского языка - leaven

I. noun see: lever Date: 14th century 1. a substance (as yeast) used to produce fermentation in dough or a liquid, a material (as baking powder) used to produce a gas that lightens dough or batter, something that modifies or lightens, II. transitive verb (~ed; ~ing) Date: 15th century to raise (as bread) with a ~, to mingle or permeate with some modifying, alleviating, or vivifying element, see: infuse