opposer

• POS: Noun
• HYPHEN: op=pos=er

CIDE DICTIONARY

opposer, n. 

 One who opposes; an opponent; an antagonist; an adversary.  [1913 Webster]

THESAURUS

opposer

adversary, antagonist, anti, bitter-ender, brawler, con, defendant, diehard, disputant, dissentient, dissident, intransigent, irreconcilable, last-ditcher, litigant, match, naysayer, negativist, noncooperator, objector, obstructionist, obstructive, oppositionist, oppugnant, plaintiff, protester, quarreler, resister, scrapper, wrangler