Wiktionary
n. An area where debate participants their representatives, and/or other interested parties attempt to "spin" or influence the perception of a debate, usually among assembled reporters.
Wikipedia
A spin room, also known as spin row or spin alley, is an area in which reporters can speak with debate participants and/or their representatives after a debate. The name refers to the fact that the participants will attempt to " spin" or influence the perception of the debate among the assembled reporters. The benefit for reporters is that they quickly get in-person interviews with debaters or their representatives, complete with audio, video and photos. For a U.S. presidential debate, the number of reporters in the spin room can number into the thousands.