Source : Webster's Revised Unabridged Dictionary (1913)

Opposition \Op`po*si"tion\, n. [F., fr. L. oppositio. See
   {Opposite}.]
   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. --Milton.

   3. Repugnance; contrariety of sentiment, interest, or
      purpose; antipathy. --Shak.

   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[deg];
      -- signified by the symbol ?; as, ? [Jupiter] [Sun],
      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.

Source : WordNet®

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"