bear

A bear - in slang, means: a big dangerous person, or a big dangerous problem

In business slang, a "bear market" is when the stock market goes down. Bears are slow and dangerous.

The opposite of a bear market is a bull market. That is when the stock market goes up. Bulls are fast and powerful. A "bear" is someone who thinks that the stock market will go down. The adjective is "bearish". For example: "He's bearish on gold." means: He thinks that the price of gold will go down.