In your own words, define an invasive species.

An invasive species is a type of organism, such as a plant, animal or microorganism, that is not native to a specific location and has a tendency to spread, which is believed to cause damage to the environment, human economy or human health. These species can be introduced to an area by ship ballast water, accidental release, and most often, by people. Once they are established in a new environment, they can outcompete native species for resources, disrupt biodiversity, and alter habitats.