Unleavened refers to a kind of bread that is made without the benefit of leavening agents also known as raising agents. The most popular of these agents being yeast, but other agents include ginger beer, kefir and the staple of the COVID 19 baker, sourdough starter.
In Jewish tradition, the term unleavened applies directly to the story of Exodus. The Jews had to leave Egypt to so quickly that the bread could not rise. It is also an edict that on Passover we eat unleavened bread. In an article in the Forward Professor David Kraemer makes the case that bread is a product of both biological culture (yeast and sourdough starters) but also the culture of man. He goes on to further explain that bread perhaps originated with the Egyptians and that in some sense ‘unleavened’ meant not only to not use the leavening agent but also that “that Egyptian culture be left behind.”