Third World vs aggregation

Third World and aggregation both are nouns.

Word	Noun	Adjective	Verb	Adverb
Third World	Yes	No	No	No
aggregation	Yes	No	No	No

As nouns, aggregation is a hypernym of Third World; that is, aggregation is a word with a broader meaning than Third World:

Third World: underdeveloped and developing countries of Asia and Africa and Latin America collectively
aggregation: several things grouped together or considered as a whole

Other hypernyms of Third World include accumulation, assemblage, collection.

Third World (noun)	aggregation (noun)
underdeveloped and developing countries of Asia and Africa and Latin America collectively	the act of gathering something together
	several things grouped together or considered as a whole