A rebuttal is a reply that a party in a suit gives during a trial to try to refute a claim or argument made by the opposing party.
Rebuttals are often made with evidence. So, for example, an attorney may present a piece of evidence in a rebuttal that disproves the opposing counsel's claim.
Rebuttals tend to be short. This is because they do not establish an argument. Instead, they simply attempt to quickly prove that the opposing counsel's argument is incorrect or not sound. For example, if a prosecutor tries to claim that the defendant was at the scene of the crime while it took place, the defense attorney may make a rebuttal proving otherwise. He or she could do this by providing evidence that the defendant was in fact somewhere else. Evidence that could prove this could be a photo taken of the defendant at an event somewhere else that took place while the crime was occurring.