Imperfect Market

A market where information is not quickly disclosed to all participants in it and where the matching of buyers and sellers isn't immediate. Generally speaking, it is any market that does not adhere rigidly to perfect information flow and provide instantly available buyers and sellers.

Investopedia Says:
The perfect market, as defined in economic textbooks, is not a truly achievable goal, but is still a beneficial model that provides a starting point for observation of our present market status. Practically, the imperfect market is the only kind that really exists. Even in the United States, the most advanced financial market in the world, there are still numerous cases of price corruption, improperly disseminated information and other market inefficiencies.

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Market in which some of the producers and/or consumers are significant enough to affect the price and quantity of goods by their actions alone.

One where imperfect competition exists. Imperfect competition includes monopoly and oligopoly with one or more sellers controlling the market price. See also Perfect Markets.