Open Market

The phrase "open market" describes an economic system like free trade. It can also mean banks trading assets. 
Economic Theory.
In economics, a market is open if the government doesn't have very many rules for the market, if a lot of competition is possible, if there aren't many tariffs, and if there aren't traditions that make it harder to do trade.An open market also means one where no one has a monopoly and where there isn't any protectionism.
In Banking.
In banking, open market operations means when a bank decides to but or sell government bonds.