An order placed with a broker/exchange to buy or sell once the security reaches a certain price. A stop-loss is designed to limit an investor's loss on a security position. Setting a stop-loss order for 10% below the price at which you bought the stock will limit your loss to 10%. For example, let's say you just purchased an alt at $100 a coin. Right after buying the coin you enter a stop-loss order for $90. This means that if the stock falls below $90, your shares will then be sold at the prevailing market price.