The slang word “tank” is a term that was adopted from the traditional financial markets and describes a strong negative financial performance of a particular asset. Therefore, an asset is said to be “tanking” when its price is falling very rapidly. The term tank may also be used to refer to a particular industry or company that is not performing well.
Another common usage of the word, especially in traditional markets, is that an asset or portfolio is considered to be “in the tank” if its financial performance over a longer period of time is declining significantly in value.
The expression “tanking” is often used as the opposite of “rallying” - very similar to how the terms “dumping” and “pumping” are used. An asset is rallying (or pumping) when it experiences a rapid short-term increase in value, whilst a tanking (or dumping) refers to the opposite when market prices present a sharp and quick decline.
Another related term to tanking is “bleeding”, which also refers to a decline in market prices. However, bleeding often describes a slower drop that takes place on a prolonged period, rather than a quick and sharp one.