/ ˈekstɜːn; NAmE -tɜːrn/ noun
( US ) a person who works in an institution but does not live there, especially a doctor or other worker in a hospital
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WORD ORIGIN
mid 16th cent. (as an adjective in the sense external ): from French externe or Latin externus , from exter outer. The word was used by Shakespeare to mean outward appearance ; current noun senses date from the early 17th cent.