The Collaborative International Dictionary of English v.0.48:

Oppose \Op*pose"\, v. t. [imp. & p. p. Opposed; p. pr. & vb.
   n. Opposing.] [F. opposer. See Ob-, Pose, and cf.2d
   Appose, Puzzle, n. Cf.L. opponere, oppositum.]
   1. To place in front of, or over against; to set opposite; to
      exhibit.
      [1913 Webster]

            Her grace sat down . . .
            In a rich chair of state; opposing freely
            The beauty of her person to the people. --Shak.
      [1913 Webster]

   2. To put in opposition, with a view to counterbalance or
      countervail; to set against; to offer antagonistically.
      [1913 Webster]

            I may . . . oppose my single opinion to his.
                                                  --Locke.
      [1913 Webster]

   3. To resist or antagonize by physical means, or by
      arguments, etc.; to contend against; to confront; to
      resist; to withstand; as, to oppose the king in battle; to
      oppose a bill in Congress.
      [1913 Webster]

   4. To compete with; to strive against; as, to oppose a rival
      for a prize.
      [1913 Webster]

            I am . . . too weak
            To oppose your cunning.               --Shak.
      [1913 Webster]

   Syn: To combat; withstand; contradict; deny; gainsay; oppugn;
        contravene; check; obstruct.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

opposed \opposed\ ([o^]p*p[=o]zd"), opposing \opposing\
   ([o^]p*p[=o]"z[i^]ng),adj.
   1. characterized by active opposition; as, two bitterly
      opposing schools of thought.

   Syn: antagonistic, antipathetic, antipathetical, opponent.
        [WordNet 1.5]

   2. acting in opposition to; as, the opposing sector of the
      same muscle group.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

opposing
    adj 1: characterized by active hostility; "opponent (or
           opposing) armies" [syn: opponent, opposing]