Short answers, pulled from the story.
The word ecumenopolis was invented in 1962 by the Greek city planner Constantinos Apostolou Doxiadis. He coined it to describe the theoretical endpoint of urbanization: a single continuous worldwide city formed by the eventual merging of all urban areas and megalopolises.
Ecumenopolis refers to a planet-spanning city used as a setting in science fiction. Notable examples include Trantor in Isaac Asimov's Foundation series (1942), Coruscant in the Star Wars franchise (1999), Giedi Prime in Dune, and Cybertron in the Transformers franchise.
Doxiadis placed ecumenopolis at the fifteenth level of ekistic units, designating it the uppermost echelon of his classification of human settlements. He considered it the most significant level because it represented the theoretical maximum scale of urban development.
Coruscant is a fictional city-planet in the Star Wars franchise, introduced in 1999, that depicts an ecumenopolis. It serves as the capital of the Galactic Republic and later the Empire, and is home to the Jedi Order. Its appearance popularized the ecumenopolis concept in mainstream culture.
Nylonkong is a term coined by Time magazine in 2008 to link New York City, London, and Hong Kong as the eperopolis hubs of the Americas, Euro-Africa, and Asia-Pacific respectively. Doxiadis defined an eperopolis as a continent-spanning city, one step below a full ecumenopolis in his hierarchy.
In Warhammer 40,000, Earth is depicted in the far future as a vast, Gothic-style ecumenopolis divided into continent-scale districts housing different branches of society and government. This version of Earth is the focus of the Siege of Terra storyline within the Horus Heresy novel series.