A "cupful" is a measurement that refers to the amount of a substance that can fit into a standard cup. In cooking and baking, it is commonly used to measure ingredients like flour, sugar, or liquids. A standard cup is typically equivalent to 8 fluid ounces in the United States. In recipes, a cupful can help ensure the right proportions of ingredients, which is essential for achieving the desired taste and texture. Different types of cups, such as measuring cups or coffee cups, may vary in size, so it's important to use the correct type when following a recipe.