Definition
A descent in which an aircraft has reached the maximum speed it can attain in a vertical or near-vertical dive, where the drag acting on the aircraft equals the combined force of gravity and any thrust, so the aircraft no longer accelerates and falls at a constant speed.
Plain English
A straight-down (or nearly straight-down) descent where the aircraft has hit its top falling speed and can't go any faster, because air resistance has caught up with the pull of gravity.
Context Anchor
Seen in discussions of parachutes, falling objects, emergency equipment, and descent physics.
Derivation
Terminal' comes from the Latin terminus, meaning 'end' or 'limit.' Here it points to the limit speed — the end of acceleration. The aircraft can't go faster in that dive no matter how long it falls.
Why Pilots Care
Knowing this speed helps predict impact forces and recovery options when an aircraft or person is falling without lift.
Analogy
A skydiver speeds up after leaving the airplane, but only until the air pushing back balances the pull of gravity. After that, the skydiver keeps falling at about the same downward speed until body position or a parachute changes it.
Grounding Statement
Picture a dropped object that speeds up at first, then reaches a steady falling speed because the air is pushing back as hard as gravity is pulling it down.
Intuition Check
Do not read terminal as meaning an airport terminal or a final approach. Here it means the limiting steady speed reached during the descent.
Example Sentence 1
The test pilot pulled out of the dive well before the aircraft approached terminal velocity descent.
Example Sentence 2
After the structural failure the fuselage stabilized in terminal velocity descent.