From The Collaborative International Dictionary of English v.0.48:
Civilian \Ci*vil"ian\, n. [From Civil]
1. One skilled in the civil law.
[1913 Webster]
Ancient civilians and writers upon government.
--Swift.
[1913 Webster]
2. A student of the civil law at a university or college.
--R. Graves.
[1913 Webster]
3. One whose pursuits are those of civil life, not military
or clerical.
[1913 Webster]