Definition of Bull Market
A bull market is a stock market where the overriding expectation is for share prices to rise. A bull market invariably means that prices are already rising. Bull markets tend to be self fulfilling as the expectations of price rises encourages people to buy now.
Bull markets can become overly optimistic and divorced from economic fundamentals. This can lead to asset bubbles. These boom and bust in share prices have often cause economic problems
Bull Market vs Bear market
Whereas a bull expects prices to rise a bear expects prices to fall. See: Bear markets