The bull symbolizes fighting ability and male fertility while the symbol of the bull stands for valor and magnanimity ever since the prehistoric times.
The bull symbol represents heaven in Babylonia and Syria with the god of storm riding on its back. In Egypt it is a symbol of royalty and is sacrificed in religious rituals for millennia, associated with the sun, fire, resurrection, earth, water, night and even death. Since its blood is used in sacrifices, it is associated with the death of winter and the return of spring; they are emblems of death, tyranny, ferocity, brutality, stubbornness, lust, and the Devil. The jumping of man over bulls shows the mans superiority over animals as is seen in Ancient Crete but on the contrary leading a bull to the arena sometimes symbolizes when Christ was led to the cross.
Since the bull has different colors, black bulls were associated with death as in Egypt where god Osiris' body was borne on the back of a black bull while In Indonesia and India bodies of princes were cremated in coffins baring shapes of bulls. The wild nature of the bulls, its roar, the windy breath and the sound of his hooves were associated to tempests, thunder, wind and ocean respectively. This made them be seen as sea gods like Poseidon, Adad, Thor, and Ishkur who were depicted as riding bulls.
Bull symbolizes strength and fertility in Hinduism. The cow here represents a fruitful earth while the bull is the fertile sky. The Rig-Veda associated the bull to a heavenly creature that fertilized the earth with his sperm. This bull was known as bull Rudra. They called their god Agni mighty bull while the bull-god Vrishabha was known to be responsible for the spinning of the cosmic wheel. The Nandi bull symbolizes sexual energy when ridden by Shiva but this energy is transformed at times to spiritual energy. In India Shiva's white bull stands for cosmic order, strength and justice. In some cultures the violent earthquakes are caused since celestial bull is believed to carry the world upon its horns and at times gets rowdy.