Bulls in dreams commonly point to stubbornness and a drive that pushes forward regardless of obstacles. A charging bull can reflect anger or determination you've been holding back, while a bull you manage to stand your ground against may suggest you're learning to meet forceful situations without simply reacting. The dream often asks where persistence has quietly tipped into rigidity.
He who is naturally well affected unto Astrology shall verily pronounce more certain Judgments. - William Lilly (1602.-1681.)