Stop Loss :

This is an instruction from a trader to a broker to stop a trade when the price reaches a certain level. It is used in order to limit losses as much as possible.

stop-loss :

An order to unwind a position when the price moves against you. For example, you had purchased a stock, the stop-loss order would be to sell the stock when the price falls to a specified level. If you were short the asset, the stop-loss would trigger a purchase.