chemtrail /ˈkɛmtɹeɪl/noun 1verb 1forms 3 noun[in the plural]1 •A contrail consisting of chemicals or biological agents deliberately sprayed at high altitudes, according to certain conspiracy theories.You and me watching / Chemtrails is where we belong / That's what I mean when we talk in this jetstream — 2008 verb1 •To spray a contrail of this kind. formschemtrailed · chemtrailing · chemtrails