From The Collaborative International Dictionary of English v.0.48 :
Hybridization \Hy`brid*i*za"tion\, n.
The act of hybridizing, or the state of being hybridized.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
hybridization
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]