A system used to place a market order. A market order is one the investor wants executed immediately at the best prevailing price. The market order to buy requires a purchase at the lowest offering (asked) price, and a market order to sell requires a sale at the highest (bid) price. The bid price is what the dealer is willing to pay for the stock, while the ask price is the price at which the dealer will sell to individual investors. The difference between the bid and ask prices is the spread. See Bid-and-Quotations.