Vis·by (vĭz'bē, vēs'bü) A city of southeast Sweden on western Gotland Island on the Baltic Sea. It was a member of the Hanseatic League and a commercial center from the 10th to the 14th century but declined after its capture by the Danes in 1362. Visby was a pirate stronghold for the next two centuries and passed to Sweden in 1645. It is a resort and an industrial center. Population: 22,200.