oligopoly
noun [ C or U ]
uk/ˌɒliˈɡɒpəli/ usplural oligopolies ECONOMICS
a situation in which only a small number of companies are involved in producing a particular type of goods or in providing a particular type of service. The group of companies itself is also referred to as an oligopoly:
Some say that Swedish banking is an oligopoly: the big four banks control 89% of total banking assets.
Compare
monopoly