oat

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of various grasses of the genus Avena, especially A. sativa, widely cultivated for their edible grains.
2. n. The grain of any of these plants, used as food and fodder.
3. n. Archaic A musical pipe made of an oat straw.

Century Dictionary and Cyclopedia

1. n. A cereal plant, Avena sativa, or its seed: commonly used in the plural in a collective sense. The oat was already in cultivation before the Christian era, and is sown in a variety of soils in all cool climates, degenerating toward the tropics, yet not ripening quite as far north as barley. Oats are grown chiefly as food for beasts, especially horses, being most largely so used in the United States: but they also form an important human food (especially in Scotland, of late years somewhat in the United States), in point of nutrition ranked higher by some than ordinary grades of wheat flour. (See oatmeal, groats, and sowens.) All the varieties of the ordinary cultivated oat are referred to A. sativa, but this is believed by many to be derived from the wild oat, A. fatua. The race called naked oat, sometimes regarded as a species, A. nuda, differs from other sorts in having the seed free from the glume. It is successful in Ireland, etc., but not in America. A variety well approved in both hemispheres is the potato-oat, with a large white plump grain, the original of which was found growing accidentally with potatoes. The black Poland is another esteemed variety; the Tartarian and the Siberian are recommended for poor soils. The varieties are numerous, new ones constantly appearing.
2. n. Any species of Avena. The wild oat of Europe, A. fatua, is a weed of cultivation in many places; in California, where it abounds, it is extensively utilized as hay. The animal, fly, or hygrometric oat, A. sterilis, native in Barbary, has two long, strong, much-bent awns, which twist and untwist with changes of moisture, and so become a means of locomotion. Various species are more or less available for pasture.
3. n. A musical pipe of oat-straw; a shepherd's pipe; hence, pastoral song. See oaten pipe, under oaten.
4. n. Bromus secalinus.
5. n. Pharus latifolius.
6. To feed with oats; feed oats to.

Wiktionary

1. n. uncountable Widely cultivated cereal grass, typically Avena sativa.
2. n. countable Any of the numerous species, varieties, or cultivars of any of several similar grain plants.
3. n. usually as plural The seeds of the oat, harvested as a food crop.

GNU Webster's 1913

1. n. (Bot.) A well-known cereal grass (Avena sativa), and its edible grain, used as food and fodder; -- commonly used in the plural and in a collective sense.
2. n. obsolete A musical pipe made of oat straw.

WordNet 3.0

1. n. seed of the annual grass Avena sativa (spoken of primarily in the plural as `oats')
2. n. annual grass of Europe and North Africa; grains used as food and fodder (referred to primarily in the plural: `oats')