Source : Webster's Revised Unabridged Dictionary (1913)

Polygenic \Pol`y*gen"ic\ (-j[e^]n"[i^]k), a. (Biol.)
   Of or relating to polygeny; polygenetic.

Source : WordNet®

polygenic
     adj : of or relating to an inheritable character that is
           controlled by several genes at once; of or related to
           or determined by polygenes