Any country or region that adopts a strategy of reducing its dependence on world or regional trade or on economic and military alliances may be isolationist. It may not take any role in the deliberations of international organizations, although nominally it might be a member. It may not honour previously signed mutual-defence treaties. In another sense, an isolationist policy is one that results in the world knowing that a nation or region has no other interest than its own. It pursues this unswervingly, manipulating whatever international interactions it has to serve this end.
The USA, between the two world wars, was isolationist; and this contributed to the failure of the League of Nations. The Republic of China in Taiwan has elected a degree of political isolationism by only maintaining diplomatic relations with a limited number of nations. There are many kinds of isolationism and many degrees. The word has also been associated with Eurocentric attitudes, particularly in the EEC/EU.
The countries of eastern Europe during their period of socialism were isolated from the mainstream of world civilization.