That depends a great deal on who is talking or typing, in what era, and where. Here's a brief list of some of the OED options for meaning:

* A foreigner, one whose language and customs differ from the speaker's.

* One not a Greek.

* One living outside the pale of the Roman empire and its civilization, applied especially to the northern nations that overthrew them.

* One outside the pale of Christian civilization.

* (With the Italians of the Renascence) One of a nation outside of Italy.

* A rude, wild, uncivilized person.

* (in mid 1800s) Applied by the Chinese contemptuously to foreigners.

* An uncultured person, or one who has no sympathy with literary culture.

* A native of Barbary.

Which one (or three) apply here can be left as an exercise for the reader.

Anyone who talks like a barbarian. In some tales the ancient Greeks thought that anyone who lived outside their city states sounded like bleating sheep. True or not, the word did mean someone who talks like a foreigner.

No kidding. That's not an ok word to be putting in a headline

In this context it means they invaded the Roman empire.