Schaulustiger

"Schaulustiger" is a combination of "Schau" -- from "schauen," to look -- and a form of "Lust" -- a word which indicates a want, an inclination or a desire (but not necessarily the erotic kind). Taken together, one might think it describes someone who likes to look at things, but it really just means the person is watching. It can be translated as onlooker, watcher, or if it refers to people in traffic slowing down to look at an accident and causing a huge jam behind them, a rubbernecker.