When the Jews were fleeing Egypt, they didn't have time to let their bread rise, so it was thus unleavened. That's why folks eat Matzoh on Passover, to remind them of this experience. Passover Matzoh is unleavened.
made without leavening; "unleavened bread is often simply flour mixed with water"
Describes baked goods that do not contain leavening agents such as baking powder, baking soda or yeast.
The word which describes any baked good that has no leavener, such as yeast, baking powder or baking soda.
Baked goods that contain no agents to give them volume, such as baking powder, baking soda, or yeast.