WordNet (r) 3.0 (2006):

interbreeding
    n 1: (genetics) the act of mixing different species or varieties
         of animals or plants and thus to produce hybrids [syn:
         hybridization, hybridisation, crossbreeding,
         crossing, cross, interbreeding, hybridizing]
    2: reproduction by parents of different races (especially by
       white and non-white persons) [syn: miscegenation,
       crossbreeding, interbreeding]