op·po·si·tion /ˌɑpəˈzɪʃən/
 反對,對抗,對立;阻力,反對派,反對黨
 Op·po·si·tion n.
 1. The act of opposing; an attempt to check, restrain, or defeat; resistance.
    The counterpoise of so great an opposition.   --Shak.
    Virtue which breaks through all opposition.   --Milton.
 2. The state of being placed over against; situation so as to front something else.
 3. Repugnance; contrariety of sentiment, interest, or purpose; antipathy.
 4. That which opposes; an obstacle; specifically, the aggregate of persons or things opposing; hence, in politics and parliamentary practice, the party opposed to the party in power.
 5. Astron. The situation of a heavenly body with respect to another when in the part of the heavens directly opposite to it; especially, the position of a planet or satellite when its longitude differs from that of the sun 180°; -- signified by the symbol ░; as, ░ opposition of Jupiter to the sun.
 6. Logic The relation between two propositions when, having the same subject and predicate, they differ in quantity, or in quality, or in both; or between two propositions which have the same matter but a different form.
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From: WordNet (r) 2.0

 opposition
      n 1: the action of opposing something that you disapprove or
           disagree with; "he encountered a general feeling of
           resistance from many citizens"; "despite opposition from
           the newspapers he went ahead" [syn: resistance]
      2: the relation between opposed entities [syn: oppositeness]
      3: the act of opposing groups confronting each other; "the
         government was not ready for a confrontation with the
         unions"; "the invaders encountered stiff opposition" [syn:
          confrontation]
      4: a contestant that you are matched against [syn: opponent,
         opposite]
      5: a body of people united in opposing something
      6: a direction opposite to another
      7: an armed adversary (especially a member of an opposing
         military force); "a soldier must be prepared to kill his
         enemies" [syn: enemy, foe, foeman]
      8: a political party opposed to the party in power and prepared
         to replace it if elected; "Her Majesty's loyal opposition"