Third Market Maker

See: Market Maker.

Some stock markets use market makers to maintain liquidity. These companies each have responsibility for a particular stock and, working from their own storehouse of shares, they buy and sell as needed to keep the market humming.

Third market makers are third-party dealers who perform a similar task. They will buy or sell stocks from clients when there isn't an exact match on the other side of the trade.

If regular market makers are like the cops, doing the job professionally, third market makers are more like the neighborhood watch, doing the job as a side pursuit. Except, in this case, the third market makers can make a profit off the transactions under the right circumstances.