ex·og·a·my 
(ĕk-sŏgə-mē)
(ĕk-sŏgə-mē)n.
1. Anthropology The custom of marrying outside the tribe, family, clan, or other social unit.
2. Biology The fusion of gametes from individuals that are not closely related, as in outbreeding.
ex·oga·mous (ĕk-sŏgə-məs) adj.