Third-world

noun, (sometimes lowercase)
1.
the underdeveloped nations of the world, especially those with widespread poverty.
2.
the group of developing nations, especially of Asia and Africa, that do not align themselves with the policies of either the U.S. or the former Soviet Union.
3.
the minority groups within a nation or predominant culture.
noun
1.
the less economically advanced countries of Africa, Asia, and Latin America collectively, esp when viewed as underdeveloped and as neutral in the East-West alignment Also called developing world

Third World definition

The nonaligned nations — which are often developing nations — of Africa, Asia, and Latin America. They are in a “third” group of nations because they were allied neither with the United States nor with the former Soviet Union.
Underdeveloped or developing countries, as in The conditions in our poorest rural areas resemble those in the third world. This expression originated in the mid-1900s, at first denoting those countries in Asia and Africa that were not aligned with either the Communist bloc nations or the non-Communist Western nations. Because they were for the most part poor and underdeveloped, the term was transferred to all countries with those characteristics, and later still to poorer groups within a larger prevailing culture.