undesirable state of society
A dystopia is the opposite of a utopia, and can mean a utopia that has become corrupt. This can be seen in George Orwell's book 1984. and Aldous Huxley's book Brave New World. A dystopia often has many problems, such as poverty, pollution, or a cruel ruler.
A frequent theme is a place that is supposed to be a beautiful and perfect utopia, but where something unforeseen ruins it.