polygamy

from WordNet (r) 3.0 (2006)

polygamy
    n 1: having more than one spouse at a time

from The Collaborative International Dictionary of English v.0.48

Polygamy \Po*lyg"a*my\, n. [Gr. ?; cf. F. polygamie.]
   1. The having of a plurality of wives or husbands at the same
      time; usually, the marriage of a man to more than one
      woman, or the practice of having several wives, at the
      same time; -- opposed to monogamy; as, the nations of the
      East practiced polygamy. See the Note under {Bigamy}, and
      cf. {Polyandry}.
      [1913 Webster]

   2. (Zool.) The state or habit of having more than one mate.
      [1913 Webster]

   3. (Bot.) The condition or state of a plant which bears both
      perfect and unisexual flowers.
      [1913 Webster]

from The Devil's Dictionary (1881-1906)

POLYGAMY, n.  A house of atonement, or expiatory chapel, fitted with
several stools of repentance, as distinguished from monogamy, which
has but one.

from Bouvier's Law Dictionary, Revised 6th Ed (1856)

POLYGAMY, crim. law. The act of a person who, knowing he has two or more 
wives, or she has two or more husbands living, marries another. It differs 
from bigamy. (q.v.) Com. Dig. Justices, S 5, Dict. de Jur. h.t.

from Moby Thesaurus II by Grady Ward, 1.0

20 Moby Thesaurus words for "polygamy":
      beena marriage, bigamy, common-law marriage, companionate marriage,
      concubinage, deuterogamy, left-handed marriage, levirate,
      leviration, love match, marriage of convenience, monandry,
      monogamy, monogyny, morganatic marriage, picture marriage,
      polyandry, polygyny, trial marriage, trigamy