What is the term for the mixture of water, non-fermentable material, and trace amounts of ethanol remaining after distillation?

The term for the mixture of water, non-fermentable material, and trace amounts of ethanol remaining after distillation is stillage. This byproduct usually contains the solids left over from the fermentation process, as well as water and residual liquids. Stillage can be further processed or repurposed in various ways, such as being used for animal feed or as a nutrient source in other industries. Understanding stillage is important in the context of bourbon production, as it reflects both the efficiency of the distillation process and the components that are not converted into distilled spirits.

The other terms refer to different stages or substances in the production of bourbon: 'wash' refers to the liquid that undergoes fermentation before distillation, 'slurry' typically describes a mixture of liquids and solids, and 'mash' is the grain mixture that is cooked and fermented to produce the wash before distillation. Each term represents a distinct part of the bourbon-making process, making it clear why stillage is the correct answer in this context.