Spiritually exorcism depicts a rite or ceremony deliberately designed to get rid of negativity and evil. It was specifically designed to expel evil spirits, but now has the symbolism of getting rid of negativity.
Psychological / emotional perspective: When emotion becomes unbearable, specific action needs to be taken to exorcise the bad feeling. In dreams we can find ourselves banishing evil, which gives us the clarity to function properly.
Material aspects: Dreaming of exorcism suggests that there is a situation or occurrence in waking life that needs dealing with promptly. Whether we choose to use dramatic methods is a choice we must make.