The 'death cross' is a technical indicator that occurs when a stock's 50-day moving average moves below its 200-day moving average. This is generally considered a bearish signal, as it suggests that the stock's long-term trend may be changing. In the case of Willis Towers Watson, the formation of a death cross could lead to a decline in the stock price in the short term, as investors may interpret this as a sign of weakness and potentially start considering short positions.