Noun. 1. refined sugar-a white crystalline carbohydrate used as a sweetener and preservative. sugar. caramelized sugar, caramel-burnt sugar; used to color and flavor food. lump sugar-refined sugar molded into rectangular shapes convenient as single servings.oun. 1. refined sugar-a white crystalline carbohydrate used as a sweetener and preservative. sugar. caramelized sugar, caramel-burnt sugar; used to color and flavor food. lump sugar-refined sugar molded into rectangular shapes convenient as single servings.