His rebuttal at the meeting was a perfect uppercut that knocked down the opponent's argument.

uppercut 是由 upper（上面的）和 cut（砍、击打）组成的复合词，字面意思是"向上击打"，在拳击中指"上勾拳"这一特定拳法。这里用作比喻，形容反驳像上勾拳一样有力，直接击倒对方的论点。