Delta-vee

Delta-vee (or Δv) is the measurement for change in velocity of a spaceship or other stellar object to escape gravitational forces. Usually the term is used synonymously for a ship's capability of changing its course in different maneuvers until all its power is depleted.

The 22nd century starship SS Mariposa could achieve a delta-vee of 3.7 NVP. 

When the crew of the USS Enterprise (NCC-1701-D) tried to restore the orbit of Bre'el IV's moon, a delta-vee of four kilometers per second were needed. The vessel was not able to produce that speed increase in time even with powering up the tractor beam and exceeding the recommended impulse engine's power limit by 47%.