To feel ones oats

from The Collaborative International Dictionary of English v.0.48
Oat \Oat\ ([=o]t), n.; pl. {Oats} ([=o]ts). [OE. ote, ate, AS.
   [=a]ta, akin to Fries. oat. Of uncertain origin.]
   1. (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.
      [1913 Webster]

   2. A musical pipe made of oat straw. [Obs.] --Milton.
      [1913 Webster]

   {Animated oats} or {Animal oats} (Bot.), A grass ({Avena
      sterilis}) much like oats, but with a long spirally
      twisted awn which coils and uncoils with changes of
      moisture, and thus gives the grains an apparently
      automatic motion.

   {Oat fowl} (Zool.), the snow bunting; -- so called from its
      feeding on oats. [Prov. Eng.]

   {Oat grass} (Bot.), the name of several grasses more or less
      resembling oats, as {Danthonia spicata}, {Danthonia
      sericea}, and {Arrhenatherum avenaceum}, all common in
      parts of the United States.

   {To feel one's oats},
      (a) to be conceited or self-important. [Slang]
      (b) to feel lively and energetic.

   {To sow one's wild oats}, to indulge in youthful dissipation.
      --Thackeray.

   {Wild oats} (Bot.), a grass ({Avena fatua}) much resembling
      oats, and by some persons supposed to be the original of
      cultivated oats.
      [1913 Webster]
    

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