What is "senior sophister"

Senior \Sen"ior\, n.

1. A person who is older than another; one more advanced in life.

2. One older in office, or whose entrance upon office was anterior to that of another; one prior in grade.

3. An aged person; an older.
   --Dryden.

   Each village senior paused to scan, And speak the lovely caravan.
   --Emerson.

4. One in the fourth or final year of his collegiate course at an American college; -- originally called senior sophister; also, one in the last year of the course at a professional schools or at a seminary.