1. To expel (an evil spirit) by or as if by incantation, command, rituals, or prayer; with the intention of ridding a person or place of a supposed presence or influence of evil spirits.
2. To free from evil spirits or malign influences; such as, to clear the mind of a painful or oppressive feeling or memory.
3. Etymology: driving out (an evil spirit) by prayers, ceremonies, etc.; borrowed from Old French exorciser, from Late Latin exorcizare, from Greek exorkizein, "exorcise, to bind by oath" (ex-, "out of" + horkizein, "to cause" or "to make a person swear, to administer an oath to", from horkos, "oath"; also literally, limitation, binding).

As noted above, "oath" is to be found at the etymological heart of exorcise, a term going back to the Greek word exorkizein, meaning "to swear in, to take an oath by, to conjure", and "to exorcise".

The English word "exorcise" is first recorded in English possibly before the beginning of the 15th century; and in this use, exorcise means "to call up" or "to conjure spirits" rather than "to drive out spirits"; a different sense which was first recorded in 1546.