Answer:
The scientific term that describes Arion flagellus as an invasive species introduced from another country is "exotic invasive species". Exotic invasive species refer to non-native species that have been introduced to an ecosystem outside of their natural range, and they have the potential to cause harm to the environment, economy, and/or human health. In the case of Arion flagellus, it is a species of slug that is native to Europe but has been introduced to other parts of the world, including North America, where it is considered an invasive species.