The Collaborative International Dictionary of English v.0.48:

Cross-fertilize \Cross"-fer"ti*lize\, v. t. [imp. & p. p.
   Cross-fertilized; p. pr. & vb. n. Cross-fertilizing.]
   (Bot.)
   To fertilize, as the stigmas of a flower or plant, with the
   pollen from another individual of the same species.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

cross-fertilize
    v 1: undergo cross-fertilization; become fertile [syn: cross-
         fertilize, cross-fertilise]
    2: cause to undergo cross-fertilization; "Mendel cross-
       fertilized different kinds of beans" [syn: cross-fertilize,
       cross-fertilise]