n. Faithfulness within a group of sexual partners, particularly to the other members of a polygamous relationship.
It's been my experience that when language changes, causes often succeed. … Turley uses the term "plural unions," and introduced me to a new word, "polyfidelity," being faithful to many lovers.
—Debra J. Saunders, “Polygamy debate evokes familiar 'rights' argument,” The San Francisco Chronicle, November 28, 2010
Though common descriptors used for monogamy don’t easily apply to polyamory, there is a recognizable spectrum of how open these partnerships may be. On the closed end, you might have a couple in a primary relationship who will then have one or more secondary relationships that are structured to accommodate the primary one. There’s also polyfidelity, in which three or more people are exclusive with one another.
—Sandra A. Miller, “Love’s new frontier,” The Boston Globe, January 03, 2010
1978 (earliest)
Registration for four-day conference at Kerista Village, Utopian Egalitarian Community. Topics to include polyfidelity, culture sculpture, neotrbalism, and gestalt o'rama.
—Cynthia Gorney, “Wares of Awareness,” The Washington Post, July 11, 1978