During the Cold War period Third World referred to countries which didn't align themselves to either of the power blocks the US and its allies or the Soviet Union and its allies. These nations formed the non-aligned movement. It was usually applied to the mostly developing nations of Africa, Latin America, and Asian countries.
Since that time, the term "third world" refers to developing and undeveloped countries which have large scale poverty and low levels of economic development. These countries often have dictatorships as the form of central government, and government corruption is rampant.
It also refers to portions of otherwise "first world" nations with similar characteristics: examples being nearly all Democrat-controlled major cities.
- The New American Desk Encyclopedia, Penguin Group, 1989