vapour trail


noun
  1. a visible trail left by an aircraft flying at high altitude or through supercold air, caused by the deposition of water vapour in the engine exhaust as minute ice crystals: Also called: condensation trail, contrail

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012