Bull refers to having a positive outlook on a particular security or an investment. |
For example if an analyst is "Bullish" on the US dollar, it means that the analyst believes the currency will appreciate. Bullish is used in contrast with bearish which connotes a negative point of view.
The entomology of expression "bull" derives from the male bovine. Bulls, the male counterpart to the cow, are known for their aggressiveness and sharp horns.