Collusion between at least two market makers (specialists who have been authorized to conduct trades in certain companiesÂ’ stock) to manipulate the price of a stock. Ghosting is accomplished by one firm pushing a stock price higher or lower, with the other firms following the first firmÂ’s lead. The stock is sold at the new levels, resulting in a guaranteed profit. It is illegal because market makers are required to compete against each other and create a fair marketplace.