The Collaborative International Dictionary of English v.0.48:

Crossbreed \Cross"breed`\ (-br[=e]d`), n.
   1. A breed or an animal produced from parents of different
      breeds; a new variety, as of plants, combining the
      qualities of two parent varieties or stocks.
      [1913 Webster]

   2. Anything partaking of the natures of two different things;
      a hybrid.
      [1913 Webster]

WordNet (r) 3.0 (2006):

crossbreed
    n 1: (genetics) an organism that is the offspring of genetically
         dissimilar parents or stock; especially offspring produced
         by breeding plants or animals of different varieties or
         breeds or species; "a mule is a cross between a horse and a
         donkey" [syn: hybrid, crossbreed, cross]
    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]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "crossbreed":
   Cape Colored, Eurasian, bastard, beget, breed, breed true, cattalo,
   citrange, copulate, cross, crossbred, engender, father, generate,
   get, griffe, half blood, half-bred, half-breed, half-caste,
   high yellow, hinny, hybrid, hybridize, inbreed, interbreed,
   intercross, ladino, liger, make love, mestee, mestiza, mestizo,
   metis, metisse, miscegenate, mixblood, mixed-blood, mongrel,
   mongrelize, mother, mulatto, mule, multiply, mustee, octoroon,
   outbreed, plumcot, procreate, proliferate, propagate, quadroon,
   quintroon, reproduce in kind, sambo, sire, tangelo, tigon, zebrass,
   zebrule