The Collaborative International Dictionary of English v.0.48:

Coenogamy \C[oe]*nog"a*my\, n. [Gr. ?; koino`s common + ?
   marraige.]
   The state of a community which permits promiscuous sexual
   intercourse among its members; -- as in certain primitive
   tribes or communistic societies. [Written also cenogamy.]
   [1913 Webster]