Wiktionary
n. A form of polygynous, polyandrous marriage in which more than one man and more than one woman form a family unit.
Wikipedia
Group Marriage is a 1973 sex comedy film directed by Stephanie Rothman.
Usage examples of "group marriage".
Some of the early Christians_anarchy, communism, group marriage-why even that kiss of brotherhood has a strong primitive-Christian flavor to it.
But a group marriage, such as our Long Family, combines the advantages of bachelorhood, monogamy, and polygamy, with the drawbacks of none.
But Dallas is not Boondock, and the unnatural practice of monogamy is as rooted in the American culture of the twentieth century as group marriage is rooted in the quasi anarchistic, unstructured culture of Tertius in the third millennium of the diaspora.
Some of the early Christians, anarchy, communism, group marriage - why even that kiss of brotherhood has a strong primitive-Christian flavor to it.
He tried to divert himself by thinking about the Throop family, the small sharing-clan on Quintana Island that had recently invited him to join in their group marriage.