Slippage

Slippage - The difference between the expected price of a trade and the price at which it is actually executed. Slippage often occurs in fast-moving or illiquid markets when an order can’t be filled at the desired level; the execution might “slip” to the next available price. It can be positive or negative, though traders usually worry about negative slippage (getting a worse price). Using limit orders and trading during high-liquidity periods are common ways to minimize slippage.