Illyricum

a country to the north-west of Macedonia, on the eastern shores
of the Adriatic, now almost wholly comprehended in Dalmatia, a
name formerly given to the southern part of Illyricum (2 Tim.
4:10). It was traversed by Paul in his third missionary journey
(Rom. 15:19). It was the farthest district he had reached in
preaching the gospel of Christ. This reference to Illyricum is
in harmony with Acts 20:2, inasmuch as the apostle's journey
over the parts of Macedonia would bring him to the borders of
Illyricum.