The phrase "velocity vector" refers to the speed at which an object is moving along with the direction it is moving in. It helps us understand both how fast something is going and where it is going. Full definition
Green arrows represent velocity vectors inside the mantle. (sciencedaily.com)
The ball's velocity vector describes its movement — the direction of the vector arrow marks the ball's direction of motion, and the length of the vector represents the speed of the ball. (scientificamerican.com)
To allow simultaneous ground - based observations, flight operations engineers at Ball Aerospace and the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder will perform a maneuver turning the spacecraft around to point the telescope in the forward velocity vector. (astrobio.net)