Londonistan is a nickname sometimes used to describe parts of London, England, where some people believe there are too many people with beliefs in terrorism. This means, that in some parts of London there are more people than in other parts, who disagree with the government, or who have ideas about committing acts of violence. This has caused some concern, as the government may not be able to control these people, or understand their beliefs and motivations. This could potentially create a situation where Londonistan becomes a place of terrorism, and people living there may be more likely to become involved in extremist activities.