The Collaborative International Dictionary of English v.0.48:
Moonseed \Moon"seed`\, n. (Bot.) A climbing plant of the genus Menispermum; -- so called from the crescentlike form of the seeds. [1913 Webster]WordNet (r) 3.0 (2006):
moonseed n 1: plant of the family Menispermaceae having red or black fruit with crescent- or ring-shaped seeds