To refute or rebut an argument; to point out errors in someone's claim and counter it (often used as '反駁する').
研究者は新しいデータで以前の説を反駁した。
The researcher refuted the previous theory with new data.
彼の意見には多くの反駁が寄せられた。
Many rebuttals were raised against his opinion.
答弁の中で相手の主張を具体的に反駁した。
In his response he specifically rebutted the opponent's claims.