Definition
An alternate name for the vertical speed indicator (VSI): a pitot-static flight instrument that displays an aircraft's rate of climb or descent in feet per minute by measuring the rate at which static air pressure changes as the aircraft changes altitude.
Plain English
A cockpit gauge that shows how quickly the airplane is climbing or descending, measured in feet per minute.
Context Anchor
Seen on the instrument panel and in instrument flying discussions as another name for the vertical speed indicator.
Derivation
Vertical' means up-and-down. 'Velocity' means speed in a specific direction. Together the name simply describes what the instrument shows: how fast the aircraft is moving up or down. It is the same instrument as the vertical speed indicator -- two names for one gauge.
Why Pilots Care
It enables precise control of climbs, descents, and level flight when outside visual references are unavailable.
Analogy
Think of it like a speedometer for up-and-down movement instead of forward movement.
Intuition Check
Do not read this as an altitude instrument. It shows the rate at which altitude is changing, not the altitude itself.
Example Sentence 1
After leveling off at cruise altitude, the pilot scanned the vertical velocity indicator to confirm it was reading zero.
Example Sentence 2
On final approach the vertical velocity indicator showed a steady 700 feet per minute descent.