From The Collaborative International Dictionary of English v.0.48 [gcide]:
Interbreed \In`ter*breed"\, v. t. & i.
To breed by crossing different stocks of animals or plants.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
interbreed
v 1: breed animals or plants using parents of different races
and varieties; "cross a horse and a donkey"; "Mendel tried
crossbreeding"; "these species do not interbreed" [syn:
crossbreed, cross, hybridize, hybridise,
interbreed]