noun A commissioned officer in an armed military organization, typically the highest rank before flag officer ranks (generals). It is generally found in armies, air forces or naval infantry (marines).
noun A military leader, distinct from the modern professional military rank.
noun An honorary civilian title bestowed by some southern US states, most commonly Kentucky; notably Colonel Sanders of KFC.
noun An informal title used to address an elderly man.
noun A form of address for an auctioneer, from the American Civil War practice of commanding officers organizing the public sale of seized goods.