baking powder

noun

1. any of various powders used as a substitute for yeast in baking, composed of sodium bicarbonate mixed with an acid substance, as cream of tartar, capable of setting carbon dioxide free when the mixture is moistened, causing the dough to rise.

noun

1. any of various powdered mixtures that contain sodium bicarbonate, starch (usually flour), and one or more slightly acidic compounds, such as cream of tartar: used in baking as a substitute for yeast

1. A mixture of baking soda, a nonreactive filler (such as starch), and at least one slightly acidic compound (such as cream of tartar). Baking powder works as a leavening agent in baking by releasing carbon dioxide when mixed with a liquid, such as milk or water.