Dictionary.com
Thesaurus.com

extern

American  
[ek-sturn, ik-sturn] / ˈɛk stɜrn, ɪkˈstɜrn /

noun

  1. a person connected with an institution but not residing in it, as a doctor or medical student at a hospital.

  2. a nun of a strictly enclosed order, as the Carmelites, who resides inside the convent but outside its enclosure and who chiefly goes on outside errands.


adjective

  1. Archaic. external; outer.

extern British  
/ ɪkˈstɜːn, ˈɛkstɜːn /

noun

  1. a person, such as a physician at a hospital, who has an official connection with an institution but does not reside in it

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of extern

1525–35; < Latin externus, derivative of exter, exterus. See exterior