'Exorcist' definitions:

Definition of 'exorcist'

noun

One of the minor orders in the unreformed Western Church but now suppressed in the Roman Catholic Church

noun

Someone who practices exorcism [syn: exorcist, exorciser]

From: GCIDE

Exorcist \Ex"or*cist\ (-s[i^]st), n. [L. exorcista, Gr. 'exorkisth`s: cf. F. exorciste.]
1. One who expels evil spirits by conjuration or exorcism. [1913 Webster]
Certain of the vagabond Jews, exorcists. --Acts xix. 13. [1913 Webster]
2. A conjurer who can raise spirits. [R.] [1913 Webster]
Thou, like an exorcist, hast conjured up My mortified spirit. --Shak. [1913 Webster]

Exorcist (Acts 19:13). "In that sceptical and therefore superstitious age professional exorcist abounded. Many of these professional exorcists were disreputable Jews, like Simon in Samaria and Elymas in Cyprus (8:9; 13:6)." Other references to exorcism as practised by the Jews are found in Matt. 12:27; Mark 9:38; Luke 9:49, 50. It would seem that it was an opinion among the Jews that miracles might be wrought by invoking the divine name. Thus also these "vagabond Jews" pretended that they could expel daemons.
The power of casting out devils was conferred by Christ on his apostles (Matt. 10:8), and on the seventy (Luke 10:17-19), and was exercised by believers after his ascension (Mark 16:17; Acts 16:18); but this power was never spoken of as exorcism.