The New York Stock Exchange crash that began on October 24, 1929, is commonly called Black Thursday.
On that day, panic selling produced exceptionally heavy trading on the New York Stock Exchange. A group of major bankers bought shares to support prices, helping stabilize the market temporarily. Selling returned with greater force on the following Monday and Tuesday, which became known as Black Monday and Black Tuesday.
The crash followed years of speculative buying, extensive use of margin, and rapid expansion of share prices during the 1920s. It was a major trigger of the Great Depression, although the depression also reflected banking failures, falling demand, deflation, and policy decisions. Black Thursday therefore names the opening shock of the famous Wall Street crash, not the entire economic crisis by itself.