ˌWall Street ˈCrash, the BrE AmE
the sudden large fall in the value of company ↑ share s on the US Stock Exchange in October 1929. For about two years before this, the price of shares had risen very fast, and when people realized that companies were therefore worth more than their true value, they lost confidence. The severe fall that followed led directly to the Great Depression of the 1930s.