A quick definition of Third World country:

A Third World country is a country that is not as developed as other countries in terms of their economy and politics. These countries are mostly found in Africa, Asia, Eastern Europe, the Middle East, and Latin and South America. They are also called developing countries, underdeveloped countries, or less-developed countries. The term used to describe these countries has changed over time, but they all refer to the same group of countries that need help to improve their economic and political situation.