polygynist--prophetes.ai

polygynist
  (pəˈlɪdʒɪnɪst)
  [f. as polygyny + -ist.]
  One who practises (or favours) polygyny.

1876 H. Spencer Princ. Sociol. I. iii. iv. §285 The Fuegians..are polygynists. Ibid. ix. §315 The Merovingian kings were polygynists.

Oxford English Dictionary