BIGAMY

Marrying on person while legally married to another.  The marriage in while on of the parties is already legally married is considered void and grounds for an annulment.  Technically, one who knowingly enters into a bigamous marriage is guilty of the crime of bigamy.  It is seldom prosecuted unless it is part of a fraudulent scheme to get another's property or some other felonious reason.  Occasionally people commit bigamy unintentionally, usually with the belief that their previous marriage had been fully dissolved. 

Having several wives at the same time is known as polygamy and being married to several husbands at the same time is known as polyandry.