A market plunge is a sudden and dramatic decrease in the value of stocks, bonds, or other financial instruments. The term 'DIVE' is often used to describe this phenomenon, which can be caused by a variety of factors such as economic downturns, political instability, or natural disasters. It can also be caused by a single event, such as a company's announcement of poor earnings or a government's decision to raise taxes. In any case, a market plunge can have serious consequences for investors and the economy as a whole.