[1] : The Collaborative International Dictionary of English v.0.48

opponent \oppo"nent\, n.
   1. one who opposes; an adversary; an antagonist; a foe.
      --macaulay.
      1913 webster

   2. one who opposes in a disputation, argument, or other
      verbal controversy; specifically, one who attacks some
      thesis or proposition, in distinction from the respondent,
      or defendant, who maintains it.
      1913 webster

            how becomingly does philopolis exercise his office,
            and seasonably commit the opponent with the
            respondent, like a long-practiced moderator --dr.
                                                  h. more.
      1913 webster

   syn: antagonist; opposer; foe. see adversary.
        1913 webster
see also:
adversary 

[2] : The Collaborative International Dictionary of English v.0.48

opponent \oppo"nent\, a. l. opponens, -entis, p. pr. of
   opponere to set or place against, to oppose; ob see ob- +
   ponere to place. see position.
   situated in front; opposite; hence, opposing; adverse;
   antagonistic. --pope.
   1913 webster
see also:
ob- position 

[3] : WordNet (r) 2.0

opponent
     adj : characterized by active hostility; "opponent or opposing
           armies" syn: opposing
     n 1: a contestant that you are matched against syn: opposition,
           opposite
     2: someone who offers opposition syn: adversary, antagonist,
         opposer, resister ant: agonist
see also:
opposing opposition opposite adversary antagonist opposer 
resister agonist 

[4] : Moby Thesaurus II by Grady Ward, 1.0

53 moby thesaurus words for "opponent":
   adversary, adversative, adverse, alien, antagonist, antagonistic,
   anti, antipathetic, antithetic, assailant, clashing, combatant,
   competitive, competitor, con, conflicting, contender, contestant,
   contradictory, contrary, counter, counteragent, cross,
   disaccordant, disputant, dissentient, enemy, foe, fractious,
   hostile, inimical, match, negative, noncooperative, obstinate,
   opposed, opposer, opposing, opposite, oppositional, oppositive,
   oppugnant, overthwart, perverse, recalcitrant, refractory,
   repugnant, rival, the opposition, uncooperative, unfavorable,
   unfriendly, unpropitious

Opponent >> O Words
Opponent, definition of term: Opponent
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