From Traderpedia

Definition: Used to voice an opinion in the belief that the market or some aspect of it is going to decline in price.

A trader thinks who thinks the market is likely to fall is termed bearish. This is the opposite of bullish. A bear market in stocks is one where around 80% of the issues will decline over an extended period of time. A decline of more than 20% of the value of a stock or index is considered Bearish. For example both, 1973 -1974 and 1982 -1983 were Bear markets.