A star jump was the near instantaneous movement of any starship with a star drive to another place by blasting through the space-time continuum. It might be as far away as the other side of the universe.
A ship without enough fuel to use its primary motors to escape a planet's gravity could make a jump from Mutter's Spiral to the Wrarth Galaxy. However, it was dangerous to jump from inside a planetary system because matter was carried along with the ship. Making a jump to another galaxy while on a planet's surface created a hyperspatial disturbance strong enough to create a black hole. For this reason, a star jump from an inhabited planet was a violation of both galactic law and universal law. (COMIC: Doctor Who and the Star Beast)