A feral animal or plant (from Latin: fera, 'a wild beast') is one that lives in the wild but is descended from domesticated specimens.

As with an introduced species, the introduction of feral animals or plants to non-native regions may disrupt ecosystems and has, in some cases, contributed to extinction of indigenous species. The removal of feral species is a major focus of island restoration.

 

Note:   The above text is excerpted from the Wikipedia article Feral, which has been released under the GNU Free Documentation License.