Roget's Thesaurus of English Words and Phrases by Peter Mark Roget

710. Opponent — N. opponent, antagonist, adversary; adverse party,

opposition; enemy &c 891; the other side; assailant. oppositionist, obstructive; brawler, wrangler, brangler†, disputant; filibuster [U.S.], obstructionist. malcontent; Jacobin, Fenian; demagogue, reactionist†. rival, competitor. bete noir [Fr.].