What does "borough" mean?

Borough: The collective body of citizens or inhabitants of a borough; as, the borough voted to lay a tax. Close borough, or Pocket borough, a borough having the right of sending a member to Parliament, whose nomination is in the hands of a single person. -- Rotten borough, a name given to any borough which, at the time of the passage of the Reform Bill of 1832, contained but few voters, yet retained the privilege of sending a member to Parliament.