1. Strong disagreement with a plan or policy; especially, when this is shown in active attempts to prevent something: There was general opposition by the public to the way the police were treating the demonstrators.
2. A person, a team, a business, or a group that someone is competing against: Dick, the chairman, couldn't understand why there was so much opposition to the plan by the new members of the committee.
3. The political parties in a country that are not part of the government: The opposition seems to be gaining more votes for the upcoming election.
4. A person or group that people are trying to defeat or to succeed against in a competition: Jack, the coach, urged his team not to take the opposition for granted because they had pulled upsets before.