Real Dictionary

town hall
countable noun: A town hall is a meeting at which a public or company official addresses and answers questions from members of the public or staff.
countable noun: In Britain, a town hall in a town is a large building owned and used by the town council, often as its main office. You can also use town hall to refer to the town council that uses this building.
countable noun: In the United States, especially in New England, a town hall is a building or hall used for local government business.

town hall in American English
a building in a town, containing the offices of public officials, the council chamber, etc.
noun: a hall or building belonging to a town, used for the transaction of the town's business and often also as a place of public assembly

town hall in British English
noun: the chief building in which municipal business is transacted, often with a hall for public meetings