Definition of "Tsushima"

An island in Nagasaki, Japan, between the Home Islands and Korea, now divided by early modern canals.  examples

A city in Nagasaki, Japan, coterminous with the main island of Tsushima.  examples

An archipelago in Nagasaki, Japan, surrounding the main island of Tsushima.  examples

A strait in Japan, between Tsushima Island and the Home Islands, the location of a major 1905 battle in the Russo-Japanese War.  examples