The Collaborative International Dictionary of English v.0.48:
Polygynian \Pol`y*gyn"i*an\, Polygynous \Po*lyg"y*nous\, a. (Bot.) Having many styles; belonging to the order Polygynia. [1913 Webster]WordNet (r) 3.0 (2006):
polygynous adj 1: having more than one wife at a time