Plain English Meaning
A short line on the airspeed display that shows where your speed is heading next — speeding up or slowing down — based on what it is doing right now.
Full Definition
On a glass-cockpit airspeed tape, a vertical magenta or green vector that extends from the current airspeed and predicts what the airspeed will be in approximately six seconds if the present rate of acceleration or deceleration continues.
Context Anchor
Seen on a digital flight display near the airspeed scale, especially during pitch and power changes in instrument flying.
Derivation
Airspeed means the airplane’s speed through the . comes from an older sense meaning to turn or lean in a direction. Together, airspeed trend means the direction your airspeed is moving, not just the speed it is right now.