to breed individuals of different strains of a species
Breeding of one cat to another unrelated one. 
The offspring of two animals of the same breed but unrelated. 
Cross-pollination, usually by natural means, with plants differing in genetic constitution.
Breeding of two cats together that don't have an ancestors in common for a minimum of three generations.
to cross (animals or plants) by breeding individuals of different strains but, usually, of the same breed. · to produce (a hybrid) by this method.