What is Bull ?
Bull is (noun) 1. a male of the cow family Be careful when you cross the field there’s a bull in it. to take the bull by the horns to try to deal with a difficult problem (informal.) He decided to take the bull by the horns and tell his father that he was leaving the family firm. 2. a male animal a bull walrus a bull elephant 3. a person who believes that stock market prices will rise
source: Easier English, Student Dictionary Upper Intermediate Level