Of or pertaining to the grasses which are cultivated for their edible seeds (as wheat, maize, rice, etc.), or to their seeds or grain.
Any grass cultivated for its edible grain, or the grain itself; -- usually in the plural.
Ceres (the Roman counterpart of Demeter) was goddess of grain and the fertility of the earth. From her name is derived the Latin adjective Cerealis (having to do with Ceres and the grain), from which comes our English word, cereal.