wash trade
n.— «In the natural gas case, there are examples of traders who agreed to buy the same amount of natural gas from each other in what is known as a “wash” trade, so they could report a high trade price to an industry publication whose trading reports set market prices for natural gas throughout the region.» —“Sempra Ordered to Turn Over Tapes” by Elizabeth Douglass in San Diego Los Angeles Times Aug. 9, 2006. (source: Double-Tongued Dictionary)