A stock market crash is a sudden and dramatic drop in the value of stocks traded on a stock exchange. This can happen due to a variety of factors, such as economic instability, geopolitical events, or changes in market sentiment.

A stock market crash can have severe consequences for investors, as it can wipe out significant portions of their portfolios in a short period of time. In extreme cases, a stock market crash can lead to a recession or depression, as investors panic and sell off their assets, leading to a downward spiral in stock prices.

However, it's important to note that a stock market crash is not always a negative event. For example, some investors may see it as an opportunity to buy stocks at lower prices and potentially profit when the market rebounds.

Overall, a stock market crash is a significant event that can have both negative and positive effects on investors and the broader economy.