Source : Webster's Revised Unabridged Dictionary (1913)

Cowpea \Cow"pea`\, n. (Bot.)
   A leguminous plant ({Vigna Sinensis}, syn. {V. Catjang})
   found throughout the tropics of the Old World. It is
   extensively cultivated in the Southern United States for
   fodder, and the seed is used as food for man.

Source : WordNet®

Vigna sinensis
     n : sprawling Old World annual cultivated especially in southern
         United States for food and forage and green manure [syn:
         {cowpea}, {cowpea plant}, {black-eyed pea}, {Vigna
         unguiculata}]