Any agent used to make dough rise or to have a similar effect on baked goods.

(figurative) Anything that induces change, especially a corrupting or vitiating change.

(transitive) To add a leavening agent.

(transitive) To cause to rise by fermentation.

(transitive, figurative) To temper an action or decision.

(transitive, figurative) To imbue; to infect; to vitiate.

To rise or become larger. (Can we add an example for this sense?)