Definitions for "Alien Species"
species that is not native to (i.e., not found in, unless imposed by humans) a region.
A species occurring in an area outside of its historically known natural range as a result of intentional or accidental dispersal by human activities. Also known as introduced species.
Any species, including its seeds, eggs, spores, or other biological material capable of propagating that species, that is not native to that ecosystem. [from Executive Order 13112 on Invasive Species