For technical traders, a death cross is definitely a sell sign. A death cross occurs when a shorter term moving average (such as the 50 day) crosses a longer term moving average (such as the 200 day) to the downside. Gold recently experienced such an event. However, fundamental traders are often at odds with this belief. (See article here, Yahoo Finance.)
Dolvin, Steven D., "Death Cross for Gold" (2013). All Chapters. 58.