Bitcoin has gone bust, tumbling below $8,000 this week. There's something in the charts that could have investors hitting the panic button.

Bitcoin's chart shows the cryptocurrency is nearing a "death cross." The term is used to describe a crossover of the 50-day moving average and the longer-term 200-day moving average. More specifically, it's used to illustrate when the 50-day moving average moves below the 200-day moving average — technicians often look at this pattern as a bearish sign of what's to come.