macronutrientEnglishOxford New American Dictionarymacronutrient /ˌmakrōˈn(y)o͞otrēənt, ˌmækroʊˈn(j)utriənt / ▸ noun Biology a type of food (e.g. fat, protein, carbohydrate) required in large amounts in the diet. ▪ a chemical element (e.g., potassium, magnesium, calcium) required in large amounts for plant growth and development.