Bulls are neutral mobs that make the same noises as Cows.They have a different way of attack than any other mob. Instead of following you, it will stay in it's position, move it's right leg on the ground, and charge at you, going at a fast speed. When charging, they deal high damage and they knock you into the air.
Bulls drop 0-2 raw steaks upon death.
The best thing to do, as with all explosive, fast, or/and high healthed mobs, is to use a bow. But a bow (unless its enchanted) is pretty much useless against a bull, since one of these takes 4 hits from a diamond sword to kill.
If you are using a diamond sword, try to get the 4 hits while he is charging.