Market Order
An instruction to buy or sell immediately at the best price currently available in the market.
A market order fills right away by taking whatever prices the order book offers. You get speed and a near-certain fill, but no control over the exact price. In a fast or thin market, the final price can land well away from what you saw a second earlier.
That gap is slippage. Buying a large amount with a market order eats through the book, lifting the average cost as it goes. For small, liquid trades the cost is trivial. For size, or in illiquid coins, a limit order usually protects you better.
Related terms
An order to buy or sell only at a chosen price or better, which may not fill at all.
Order BookA live, ranked list of all outstanding buy and sell orders for an asset on an exchange.
SlippageThe difference between the price you expected on a trade and the price it actually executed at.
Ask PriceThe lowest price a seller is currently willing to accept for an asset on the order book.