The USD/ZAR is what is referred to as an exotic pair in currency trading or forex trading, as the rand component (ZAR) is an emerging market currency which carries less liquidity than that of developed market currencies.
Exotic currencies, because they do carry lower liquidity than major most traded market currencies (the US dollar, Swiss franc, euro, British pound, Japanese yen, Canadian dollar and the Australian dollar), will carry a wider spread and in turn, a higher cost to trade. However, the lower liquidity does offer higher volatility and in turn, a higher reward (or loss) opportunity on offer.