mid-14c., originally of religion, from French conversion, from Latin conversionem (nominative conversatio), noun of action from past participle stem of convertere (see convert (v.)). General sense of "transformation" is early 15c. Of buildings, from 1921. Conversion disorder "hysteria" (attested from 1946 but said to have been coined by Freud) was in DSM-IV (1994).
conversion con·ver·sion (kən-vûr'zhən, -shən)
The acquisition by bacteria of a new property associated with presence of a prophage.
A defense mechanism in which repressed ideas, conflicts, or impulses are manifested by various bodily symptoms, such as paralysis or breathing difficulties, that have no physical cause.