To dream of an exorcism represents an attempt to force enormous positive change where you or someone else is consumed by a powerful negative influence. It may also reflect extraordinary measures being taken to control an addiction or dangerous manipulative influence. A powerful need to purity or cleansing in your life.
An exorcism may also reflect cutting off something dangerous "cold turkey." Preoccupation with resisting a long standing problem. Your initiative to regain control.
Example: A woman dreamed of performing an exorcism on her son. In waking life she was trying very hard to get her children back after child protection services took them away. The exorcism most likely reflected the powerful need to perfectly remove all negativity from her home life to please the bureaucracy of government that was terrifying her family life. The exorcism may also reflect her feelings about how "demonicly possessed" the government felt taking her kids away while she was desperately trying to restore sanity to her home life by proving herself to them.
*Please See Haunted