Having the character of, or dominated by, an oligopoly
1988 August 5, David Moberg, “Competing Together”, in Chicago Reader:
There was little competition in oligopolistic industries, and "Fordist" production techniques emphasized long production runs, routinized and "deskilled" work, and minimal innovation or attention to quality.
1997, Roy Porter, The Greatest Benefit to Mankind, Folio Society 2016, p. 604:
Medicine […] is in many cases no less business- and money-oriented than the great oligopolistic corporations.