noun

• (obsolete) A fortified town.
• (rare) A town or city.
• A town having a municipal corporation and certain traditional rights.
• An administrative district in some cities, e.g., London.
• An administrative unit of a city which, under most circumstances according to state or national law, would be considered a larger or more powerful entity; most commonly used in American English to define the five counties that make up New York City.
• Other similar administrative units in cities and states in various parts of the world.
• A district in Alaska having powers similar to a county.
• (historical, Britain, law) An association of men who gave pledges or sureties to the king for the good behaviour of each other.
• The area, properly called Southwark, just south of London Bridge, which is at the north end of Borough High Street (OS grid ref TQ3279).