Dissident movements are organized efforts by individuals or groups to challenge or oppose established authority, particularly in political contexts where dissent is suppressed. These movements often arise in response to authoritarian regimes and aim to promote social, political, or economic change through protests, activism, and other forms of resistance. They played a significant role in shaping the political landscape of Europe during the late 20th century, especially as Gorbachev's reforms sought to address the grievances of various dissident groups within the Soviet Union and Eastern Europe.