RhymeZone: duopoly definitions

Definitions of duopoly:

noun: (economics) A market situation in which two companies exclusively provide a particular product or service.
noun: (by extension) The domination of a field of endeavor by two people or entities.
noun: (broadcasting, by extension) Situation in which two or more TV or radio-stations in the same city or community share common ownership.

(Definitions from Wiktionary)