A reply speech is a short closing speech used primarily in the World Schools debate format. Each side gets one four-minute reply speech at the end of the round, delivered by the first or second speaker (not the third). The Opposition delivers their reply first, and the Proposition delivers theirs last.
What a Reply Speech Does
The job of a reply speech is to bias the judge toward your side by framing the entire round. It is not the place to introduce new arguments - reply speakers review what happened, explain which arguments mattered most, and argue that their side won the most important clashes.
Why the Proposition Speaks Last
In World Schools, the Proposition's reply speech comes last so that they have the final word. This is balanced out by the fact that the Proposition also spoke first - they had to commit to a definition and a case before the Opposition had said anything. Speaking last in reply compensates for speaking first in substance.