The Collaborative International Dictionary of English v.0.48:

Fagopyrum \Fagopyrum\ prop. n.
   a genus of plants of the buckwheat family, including the
   buckwheat Fagopyrum esculentum; in some classifications
   included in the genus Polygonum.

   Syn: genus Fagopyrum.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

Fagopyrum
    n 1: buckwheat; in some classifications included in the genus
         Polygonum [syn: Fagopyrum, genus Fagopyrum]