contrail \KON-treyl\,
noun:
a visible condensation of water droplets or ice crystals from the atmosphere, occurring in the wake of an aircraft, rocket, or missile under certain conditions.
With the air over the desert as dry as it was this time of year, the target would not leave much of a contrail, if any.
-- Richard Hilton, 'Skyhammer," 2009
"Man is not merely a linear thinker," she said, drawing a line of mist in the air. It hovered like a distant contrail.
-- Piers Anthony, "On a Pale Horse", 1983
Contrail was coined in the 1940s as a portmanteau of condensation and trail to refer to the water vapor emitted by aircraft.
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