polyandry

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The condition or practice of having more than one husband at one time.
• noun Zoology A mating pattern in which a female mates with more than one male in a single breeding season.
• noun Botany The condition of having numerous stamens.

from The Century Dictionary.

• noun The state of having more husbands than one at the same time; plurality of husbands.

from the GNU version of the Collaborative International Dictionary of English.

• noun The possession by a woman of more than one husband at the same time; -- contrasted with monandry.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun : The having of a plurality of husbands at the same time; usually, the marriage of a woman to more than one man, or the practice of having several husbands, at the same time.
• noun : The mating pattern whereby a female copulates with plural males.
• noun general : Sexual relations with plural males, by a female or a male, human or non-human, within or without marriage.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun having more than one husband at a time