The phrase "firm dough" refers to a type of dough that is not very soft or elastic, but instead feels dense and solid. It requires more effort to work with and may not easily change shape. Full definition
In a large bowl combine the flour and salt; add a little water at a time to make firm dough. (archanaskitchen.com)
The ovens are provided with a device for dividing firm dough into pieces and an automatic extractor for removing the biscuits or waffles after baking. (foodprocessing-technology.com)