An order placed to execute at the current market price. A buy market order means the trader wants the order to execute for the lot size indicated at the lowest current ask price. A sell market order means the trader wants the order to execute for the lot size indicated at the highest current bid price. In contrast to a limit order, a market order executes immediately assuming you have the funds to cover the cost of the trade. Market orders are less appealing when there is a wider spread, as you assume an unrealized loss at execution. For instance, if the bid price is $8 and the ask price is $8.10, a buy market order executes at $8.10, and the at-the-market price for you to sell right away is $8.