During the cold war, a group of countries like USA, Canada, Japan, South Korea, western European nation & their allies was along NATO and they were called First World. Similarly, there were other countries like Soviet union, China, Cuba and their allies along Communist bloc and they were called Second World. And there were the countries that remained neutral, non-aligned with either NATO or the Communist Bloc and they were called third world country. So, the term Third world arose during the cold war.

The third World countries include many countries from Africa, Latin America, Oceania and Asia. Over the time, the definition of the Third world has been changed. It has been interpreted by different aspects. Since there is no more Soviet union and the cold war has ended, now the term third world has been used to describe the poor and developing countries.

Most of the third world countries are poor and underdeveloped. These countries have been suffering from the problems like low education, poor infrastructures, improper sanitation and poor health condition. So, third world and developing countries are defined as the same. However, there has been no precise definition of developing countries. The definition varies from organization to organization and there is no exact definition given by the WTO.

At the moment, third world countries have been defined based on different categories. These categories are Political rights and Civil Liberties, Gross National Income, Human development Index, Poverty and press freedom.
Third world countries in terms of Political rights and civil liberties:

These include the countries that have worst records for political rights and civil liberties. These countries have the most repressive regime in the world where even the daily life of an individual is governed by the state of the country. Any independent organization and political opposition are banned. Burma, Cuba, Libya, North Korea, Somalia, Sudan, Turkmenistan, and Uzbekistan are in this category.

Third world countries in terms of Gross National Income

This category includes the countries that have a very low Gross National income based on purchasing power parity per capita.  A country with below $1000 yearly income per capita is included in this category. Timor-Leste, Malawi, Somalia, Afghanistan, Yemen, Burundi, Ethiopia, Niger, Liberia etc are listed in this group.

Third world countries in term of Human development Index

Every year, UN published Human Development index. HDI is the measure of healthy life, education level, and the GNI. So, the countries with least HDI are under this category. Kenya, Nepal, Pakistan, Bangladesh, Senegal, Haiti, Uganda, Ethiopia, Mali, Guinea, Chad, Niger, Burundi etc are under this category.

Third world countries in term of Poverty

UN identifies the list of least developed countries on the basis of GNI, weak human assets, and economic stability. There are 50 countries that are listed as least developed countries. Angolo, Mali, Rwanda, Uganda, Afghanistan, Timor-Leste, Haiti, Kiribati etc are some of the least developed countries.

Third world countries in term of press freedom

This category includes the countries that have very poor press freedom. In this country, privately owned media is not allowed and freedom of expression does not exist. Tunisia, Maldives, Pakistan, Iraq, China, Nepal, Cuba, Iran, North Korea etc are some of the countries under this list.

So, if we analyze data and interpretation regarding third world countries, then Nepal is surely a third world country.