Source : Webster's Revised Unabridged Dictionary (1913)

Moonseed \Moon"seed`\, n. (Bot.)
   A climbing plant of the genus {Menispermum}; -- so called
   from the crescentlike form of the seeds.

Source : WordNet®

moonseed
     n : plant of the family Menispermaceae having red or black fruit
         with crescent- or ring-shaped seeds