Yeasty
Part of speech: adjective
Definition: Having or resembling yeast. Foamy and frothy. Emotionally bubbling over (as with exuberance) Trivial.
Leaven
Part of speech: noun
Definition: Any agent used to make dough rise or to have a similar effect on baked goods.
Part of speech: verb
Definition: To add a leavening agent.To cause to rise by fermentation.To temper an action or decision.