Tim Bowen sheds some light on the origins and definition of the phrase to take the bull by the horns.

This expression probably originated in the American West where it was a common, but dangerous, practice to wrestle with steers. This was not only done for entertainment at rodeos but was part of the everyday working life of ranchers and cowhands throughout the west. To control a bull or a steer (a young bull) the cowhand would first have to catch it. Trying to grab the neck or legs of a dangerous creature like this was not an option. The only solution was to take a deep breath and face the problem directly by grabbing the bull by the horns and then pulling it to the ground. This expression now means to confront a problem directly without “beating about the bush”.