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I too have always considered civilians to be all that were not in the military. Guess there are other definitions. From dictionary.com.

civilian[ si-vil-yuhn ]
noun
1. a person who is not on active duty with a military, naval, police, or fire fighting organization.
2. anyone regarded by members of a profession, interest group, society, etc., as not belonging; nonprofessional; outsider: We need a producer to run the movie studio, not some civilian from the business world.
3. a person versed in or studying Roman or civil law.