1. A frothy, GELATIN-based dessert that has been lightened by the addition of beaten egg whites. Sometimes whipped cream is added, though it makes the dessert richer and not as airy. Sponges may be variously flavored, usually with fruit purees.
2. A light bread-dough mixture made by combining the yeast with some of the flour and liquid called for in a recipe. The thick, batterlike mixture is covered and set aside until it bubbles and becomes foamy, which, depending on the combination of ingredients, can take up to 8 hours. During this time, the sponge develops a tangy flavor. The remaining ingredients are added to this sponge and the bread is kneaded and baked as usual. Using a sponge also makes the final loaf slightly denser.

This definition is in context to Food. See more contextual defintions for Sponge.