From Longman Dictionary of Contemporary Englishleavenleav‧en1 /ˈlevən/ (also leavening /ˈlevənɪŋ/) noun 1 [uncountable] technicalDFC a substance, especially yeast, that is added to a mixture of flour and water so that it will swell and can be baked into bread → unleavened2 [singular, uncountable] literaryINTERESTINGHAPPY something that makes an event or situation less boring, serious, or sad
Examples from the Corpus
leaven• A piece of dough was kept back after using the yeast and this is called leaven.• None rejoice more in this leaven than the professional scholars themselves.• This leaven was added the next time baking bread was done.leavenleaven2 verb [transitive] formalINTERESTINGBORING to make something less boring, serious, or sad→ See Verb tableExamples from the Corpus
leaven• What emerges from that tainted oven will likely be a typical loaf of local politics leavened by big money.• His intellectualism now was leavened by experience.• Feminist consciousness now leavens every relationship, every single social and professional encounter.• My affection for her was leavened with lesser likings and with admiration.• Organist Dan Wall's power is leavened with subtlety and his four compositions are perfect vehicles for Abercrombie.Origin leaven1 (1300-1400) Old French levain, from Vulgar Latin levamen, from Latin levare “to raise” 