1. a flag or banner, as a military or naval standard used to indicate nationality.
2. a badge of office or authority, as heraldic arms.
3. a sign, token, or emblem.
4. U.S. Navy and Coast Guard. the lowest commissioned officer, ranking next below a lieutenant, junior grade, and equal to a second lieutenant in the Army.
5. Archaic. standard-bearer (def 1). (http://dictionary.reference.com/browse/ensign)
"Regulations require that each Sunday he hoist the ensign and he does, first thing."
- M. L. Stedman, The Light Between Oceans (2012)