Definition - What does Cluster Marriage mean?
A cluster marriage is a form of group marriage in which several married couples live together and exchange partners. The couples may all consider themselves married to each other and as such form a household much like that of any other marriage, just with more people. What may distinguish cluster marriages from other group marriages in the polyamorous community is the greater likelihood for an equal number of participants of different genders, rather than the popular format of one man and multiple women.
Kinkly explains Cluster Marriage
Cluster marriages, like any group marriages are not legally recognized and as such members of them may create civil contracts or other legally binding agreements to afford participants some of the legal and financial securities they might have in a legally sanctioned marriage.