n. A jet contrail that has been laced with chemical or biological agents.
2010
Ah, the old "chemtrail conspiracy" theory. The idea that the white lines of condensed water vapor that you see following planes, contrails, are really a toxic substance intentionally being sprayed on people by the government has been around at least since 1996.
2010
Wonder how the Bush administration arranged for the destruction of the World Trade Center? Curious why the government planes are releasing toxic chemtrails into our atmosphere? Step right up, because for a record 26 days, KPFK-FM (90.7) not only provided answers but offered to hook you up with that sweet DVD set, unveiling the fuller, darker truth.
1999 (earliest)
So Levinson - and plenty of cohorts on the Internet, not to mention one well-known AM radio talk show host — are spreading the word about "chemtrails," as they call them. Levinson et al say the trails contain bacteriological pathogens and an assortment of toxic chemicals. The government is "spraying" our fair skies for dark, dark reasons.
For more than you probably want to know about the chemtrail "conspiracy," or if you simply enjoy thorough refutations (or, I guess, refudiations) of this kind of thing, see chemtrails entry in The Skeptic's Dictionary.