The opposition is the person or team you are competing against in a game of sports. It can also refer to the group of political parties in a country that is not part of the government, known as HM Opposition (or formally HM Official Opposition). The leader of this party is called the Leader of the Opposition. Opposition can also be used to describe the relationship between any alternative units within a phonological system, particularly those that differ in quantity or quality.
Webster’s New World College Dictionary, Fifth Edition Copyright