A system in which the exchange rate of the national currency is not fixed at a certain level, but at the same time the monetary authorities try to regulate it. On the one hand, small fluctuations in the exchange rate can be smoothed out by buying up the national currency if there is a threat that the rate will decline. Similarly, the currency can be sold if the exchange rate is free to rise. You can also influence the exchange rate by pursuing a certain macroeconomic policy.