The term "firm dough" refers to a stage in bread making where the dough has reached its peak consistency and is no longer sticky or wet. At this point, it should hold its shape well when pressed between your fingers. It means that the gluten strands have developed enough to provide structure and elasticity to the dough, allowing it to rise properly during baking. A firm dough is crucial for achieving a good loaf of bread with a proper crumb texture.