In the context of the markets, a massive decline in values experienced by investors and traders. When the price of securities such as stocks and other assets like cryptocurrencies, commodities and derivatives get crushed, people call it a bloodbath.
These are periods of massive selling.
It is also a time when some feel that buying could be an intelligent move. There is a saying in the investing world of "buy when there is blood in the streets". Here is where many feel a contrarian stance is beneficial.