1. the underdeveloped nations of the world, esp. those with widespread poverty.
2. the group of developing nations, esp. 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. Cf. First World, Second World, Fourth World.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.