cereal UK /ˈsɪə.ɹɪ.əl/US [ˈsiːɹiəl]noun 3adjective 1forms 1 noun3 •A type of grass (such as wheat, rice or oats) cultivated for its edible grains. •Breakfast cereal.Would you like some cereal?Which cereal would you like for breakfast? •The grains of such a grass. adjective1 •Of or relating to cereal.Millet, the smallest of all the cereal seeds cultivated for food, grows on arid soils, where rice and maize cannot be successfully cultivated, […] — 1837 formscereals