Plain English Meaning
A poisonous gas you cannot see or smell that is produced when fuel burns. In an airplane it usually comes from the engine exhaust, and if it leaks into the cabin (often through the cabin heater) it starves your body of oxygen.
Full Definition
A colorless, odorless, tasteless gas produced by the incomplete combustion of carbon-based fuels such as gasoline, oil, and wood. In aircraft, it is most often generated by the engine's exhaust system and can leak into the cabin through a faulty exhaust-based heater or cracks in the firewall. When inhaled, CO binds to the hemoglobin in the blood roughly 200 times more readily than oxygen, blocking oxygen delivery to the brain and tissues and causing symptoms ranging from headache and dizziness to unconsciousness and death.
Context Anchor
Pilots encounter CO in discussions of exhaust leaks, , , and health .