contrail -
an artificial cloud created by an aircraft; caused either by condensation due to the reduction in air pressure above the wing surface or by water vapor in the engine exhaust
Contrails (short for "condensation trails") or vapour trails are artificial clouds that are the visible trails of condensed water vapour made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets. If the air is cold enough, this trail will comprise tiny ice crystals.
OmegaWiki Dictionary
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contrail An artificial cloud made by the exhaust of jet aircraft or wingtip vortices that precipitate a stream of tiny ice crystals in moist, frigid upper air.
