Definition
The disturbed mass of air left behind a moving aircraft, consisting of turbulent airflow, vortices generated by the wingtips, and the engine exhaust stream. The wake trails behind and below the aircraft and can persist for some time after the aircraft has passed.
Plain English
The trail of churned-up, turbulent air that an aircraft leaves behind it as it flies.
Context Anchor
Seen in aircraft powerplant, propeller, and airflow discussions when describing how air moves around or behind aircraft parts.
Derivation
From the Old Norse 'vok' meaning a hole or opening in ice, later applied to the track a ship cuts through water. Aviation borrowed the word directly from nautical use because an aircraft leaves a similar trail of disturbed air, just as a ship leaves a trail of disturbed water.
Why Pilots Care
An aircraft's wake — especially the wingtip vortices — can be powerful enough to roll or upset a smaller aircraft following too closely. Knowing where the wake goes is a safety issue on takeoff, landing, and en route behind heavy aircraft.
Analogy
Like the trail of churned water behind a boat. You can't see it from a distance, but a smaller boat crossing it will feel the bumps long after the larger boat has passed.
Intuition Check
Wake does not mean waking up from sleep here. It means the disturbed trail left behind as something moves through air.
Example Sentence 1
The tower instructed the small Cessna to wait two minutes before departing to allow the wake from the departing 737 to dissipate.
Example Sentence 2
Pilots must account for wake turbulence when following another aircraft on approach.