means A rebuttal is a counter-argument that answers and tries to disprove a claim, especially one made against you.

from From the Old French 'reboter' or 'rebuter,' meaning to thrust or drive back — built from 're-' (back) plus 'boter' (to push or strike), the same root that gives English 'butt' as in a ram's headbutt. So a rebuttal is, quite literally, you butting an argument back where it came from. It entered English first as a legal term, the formal pushing-back of an opponent's case, before spreading to any dispute where someone shoves a claim back across the table.