Biblical Marriage is misleading: Polygyny, Open Marriage, Woman marrying rapist, levirate marriage are all biblical.

http://www.alternet.org/belief/why-term-biblical-marriage-misleading?akid=12414.294211.2ei7Iy&rd=1&src=newsletter1025015&t=19

First, the kinds of relationships that qualify for marriage in the Bible, and thus could count as "biblical marriage," represent quite a striking range of options. They include polygyny (more than one wife or concubine, simultaneously), open marriage for the man (since he can have access to the female slaves or servants in the house), forcing a woman to marry her rapist (Deuteronomy 22:28-29) and levirate marriage (wherein a childless widow must marry the brother of her deceased husband). Those are just a few of the examples from the Hebrew Bible.