The phrase "a rich source of dietary fiber" refers to a food or ingredient that contains an abundant amount of dietary fiber. Dietary fiber is essential for maintaining good health, as it promotes proper digestion and helps regulate blood sugar levels. Foods that are considered high in dietary fiber include fruits, vegetables, whole grains, legumes, nuts, and seeds. When a food item or ingredient is described as "a rich source of dietary fiber," it means that the food contains an ample amount of this important nutrient, making it beneficial for individuals looking to increase their daily intake of fiber.