oat

noun5

1. •
   Widely cultivated cereal grass, typically Avena sativa.

   • The oat stalks made good straw.
   • The main forms of oat are meal and bran.
2. •
   The seeds of the oat, a grain, harvested as a food crop and for animal feed.

   • […]I could munch your good dry Oates. Me-thinkes I haue a great desire to a bottle of hay: good hay, sweete hay hath no fellow. — 1595
3. •
   Any of the numerous species, varieties, or cultivars of any of several similar grain plants in genus Avena.

   • The wild red oat is thought to be the ancestor of modern food oats.
4. •
   The tiniest amount; a whit or jot.

   • Few of them care an oat for the niceties of the arrow sport, but for the young lords that may be on a hunt! — 1994
5. •
   A simple musical pipe made of oat-straw.

prepositional phrase1

1. •
   (Internet) Initialism of of all time.