Wolpertingers are a mixture of several species, in this case it's a rabbit with wings, canine teeth, and the antlers of a deer. Their origin lies in Bavaria, but similar animals are also known from other countries, for example America's Jackalope. Geralt encounters them in the Land of a Thousand Fables.
Within the Land of a Thousand Fables, the Wolpertingers are one of the few entities that receive more damage from Geralt's steel sword than that from his silver.