(1):

(n.) The state or habit of having more than one mate.

(2):

(n.) The condition or state of a plant which bears both perfect and unisexual flowers.

(3):

(n.) 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.