(1) Pertains to progeny produced by crossbreeding or by hybridization.
(2) A hybrid.
(3) Refers to an animal produced by breeding purebred parents of two different breeds, varieties, or population.
In general use, the term crossbred is more often used to refer to progenies of animal breeding whereas the term hybrid is more often used to refer to offspring from plant breeding.
In another sense, a crossbred is used when referring to a hybrid resulting from a planned cross between parents with desirable traits. A mongrel, which is a mixed-breed of unknown origin, often has less desirable traits compared with crossbred.
Related terms: crossbreed (verb), crossbreeding (noun).