资料来源 : Webster's Revised Unabridged Dictionary (1913)

Opposer \Op*pos"er\, n.
   One who opposes; an opponent; an antagonist; an adversary.

资料来源 : WordNet®

opposer
     n : someone who offers opposition [syn: {adversary}, {antagonist},
          {opponent}, {resister}] [ant: {agonist}]