cereal

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A grass such as wheat, oats, or corn, the starchy grains of which are used as food.
• noun The grain of such a grass.
• noun Any of several other plants or their edible seeds or fruit, such as buckwheat or certain species of amaranth.
• noun A food prepared from any of these plants, especially a breakfast food made from commercially processed grain.
• adjective Consisting of or relating to grain or to a plant producing grain.

from The Century Dictionary.

• Pertaining or relating to edible grain; producing farinaceous seeds suitable for food.
• noun A gramineous plant cultivated for the use of its farinaceous seeds as food; any one of the annual grain-plants, as wheat, rye, barley, oats, rice, millet, or maize.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Of or pertaining to the grasses which are cultivated for their edible seeds (as wheat, maize, rice, etc.), or to their seeds or grain.
• noun Any grass cultivated for its edible grain, or the grain itself; -- usually in the plural.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun countable A type of grass (such as wheat, rice or oats) cultivated for its edible grains.
• noun uncountable The grains of such a grass.
• noun uncountable Breakfast cereal.
• noun countable A particular type of breakfast cereal.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun grass whose starchy grains are used as food: wheat; rice; rye; oats; maize; buckwheat; millet
• noun a breakfast food prepared from grain
• adjective made of grain or relating to grain or the plants that produce it
• noun foodstuff prepared from the starchy grains of cereal grasses