economists define as a market structure with a few large firms
Market structure 2. Oligopoly, in which a market is run by a small number of firms that together control the majority of the market share.
Market economy Market economies do not logically presuppose the existence of private ownership of the means of production. A market economy can and often does include various types of cooperatives, collectives, or autonomous state agencies that acquire and exchange capital goods in capital markets. These all utilize a market-determined free price system to allocate capital goods and labor.[3] In addition, there are many variations of market socialism, some of which involve employee-owned enterprises based on self-management; as well as models that involve the combination of public ownership of the means of production with factor markets.[7]