One who opposes another; one who works or takes a position against someone or something; one who attempts to stop the progress of someone or something.
The participant who opens an academic debate by putting forward objections to a theological or philosophical thesis.
One who opposes another in words (in a dispute, argument or controversy).
One who is opposed or objects (to a policy, course of action or set of ideas).
One who opposes another physically (in a fight, sport, game, or competition).
Actions by one political group against another political group, either by using governmental power or by popular actions such as protests; generally, disagreement in politics.
A recognized political party or group of parties in multiparty political systems that is present in Parliament or some other legislative body and does not control the floor (usually due to being in the minority).
An unrecognized political party in a one-party state.