A rebuttal is a direct response to the other team's arguments. Rather than introducing new material, a rebuttal speaker focuses on attacking opposing claims - pointing out logical flaws, missing evidence, bad assumptions, or reasons why the other side's impact is smaller than their own.
When Rebuttals Happen
Some formats have dedicated rebuttal speeches at the end of the round (CNDF has a Prime Minister's Rebuttal and an Opposition Rebuttal, for example). Other formats, like World Schools, use the third speaker on each side to focus almost exclusively on rebuttal. British Parliamentary weaves rebuttal into every constructive speech after the first.
What Good Rebuttal Looks Like
Strong rebuttal is specific. Instead of saying 'their argument is wrong,' a good rebuttal says 'their argument assumes X, but X only holds under Y condition, and Y does not apply here because Z.' Judges consistently reward rebuttal that engages with the other team's best arguments, not just their weakest ones.
Rebuttal vs Clash
Rebuttal is one of the main ways clash happens in a debate. A round with lots of clash means both teams are actually responding to each other - not just reading scripts. Judges notice immediately when a speaker skips rebuttal in favor of restating their own case.