From Wikipedia:
http://en.wikipedia.org/wiki/Hindenburg_Omen

The Hindenburg Omen is a technical analysis signal that attempts to predict a forthcoming stock market crash. It is named after the Hindenburg disaster, the crash of the German zeppelin of the same name in May 1937. The Hindenburg Omen is the alignment of several technical factors that measure the underlying condition of the stock market - specifically the NYSE - such that the probability that a stock market crash occurs is higher than normal, and the probability of a severe decline is quite high.