Plain English Meaning
How fast something is moving and the direction it's moving in.
Full Definition
The speed of an object in a specified direction. In aviation, velocity is used when both how fast something is moving and which way it is moving matter — for example, the airplane's motion through the air, the relative wind, or the flow of air over a wing.
Context Anchor
Seen in discussions of airplane feel, airflow over the wings and control surfaces, and how control response changes as the airplane speeds up or slows down.
Derivation
From Latin velocitas, meaning 'swiftness' or 'speed.' In physics and aviation it picked up the added requirement of direction, which is what separates velocity from plain speed.