1. a visible trail of condensation left behind an aircraft in flight; a contrail.
Usage: informal; often used in conspiracy theories without scientific support

Examples

• The airplane left a long chemtrail across the clear blue sky.
• Some people believe chemtrails contain harmful chemicals, though scientists attribute them to water vapor.
• On cold days, you can see chemtrails forming behind high-altitude aircraft.
• The pilot watched the chemtrail dissipate slowly as the plane climbed higher.
• Conspiracy theorists often point to chemtrails as evidence of secret government programs.