1. An adult male bovine mammal of the ox and cow family: Among cows in the pasture, there is usually at least one bull.
2. The male of certain other large animals, such as the alligator, elephant, whale, or moose: The bull elephant is also a protector of the younger elephants.
An optimist, especially regarding business conditions, who buys commodities or securities in anticipation of a rise in prices or who tries by speculative purchases to effect such a rise: The bright young stockbroker was a bull when it came to making speculative purchases.
An official document issued by the pope and sealed with a "bulla" (a round seal affixed to a papal bull): The bull is an official command or statement written by the Roman Catholic Pope.
A constellation in the Northern Hemisphere near Orion and Aries known as "Taurus": Byron was born under the sign of Taurus and he had the characteristics of being large, strong, and forceful; just like a bull.
A slang term for a police officer or a detective: A German cartoon showed a policeman talking with a cow and she told him that her husband was also a bull.
The optimistic bull issued by the church created a ban on shooting a bull in the pasture which was enforced by a bull from the local police department who happened to be born under the astrological sign of the Bull.
These were all in response to the bull market in livestock trading.