bull 1 
(bl)
(bl)n.
1.
a. An adult male bovine mammal.
b. The uncastrated adult male of domestic cattle.
c. The adult male of certain other large animals, such as alligators, elephants, moose, or whales.
2. An exceptionally large, strong, and aggressive person.
3.
a. An optimist, especially regarding business conditions.
b. A person who buys commodities or securities in anticipation of a rise in prices or who tries by speculative purchases to effect such a rise.
4. Slang A police officer or detective.
5. Slang
a. Foolish, deceitful, or boastful language.
b. Insolent talk or behavior.
v. bulled, bull·ing, bulls
v.tr.
To push; force.
v.intr.
To push ahead or through forcefully: "He bulls through the press horde that encircles the car" (Scott Turow).
adj.
Idiom: 1. Male.
2. Large and strong like a bull.
3. Characterized by rising prices: a bull market.
grab/take the bull by the horns
To deal with a problem directly and resolutely.
[Middle English bole, bule, from Old English bula, probably from Old Norse boli; see bhel-2 in the Appendix of Indo-European roots.]