Shunt drive was a type of faster-than-light engine which exceeded warp drive by actually using time travel as a method of transportation through space. A ship equipped with shunt drive would "fold" time so the ship arrived at its destination instantaneously. (NF - Turnaround comic: "Part I")
Starfleet experimented with the technology, outfitting the starship Paradox with shunt drive. Although the experiments were a success, individuals from the Mirror universe stole the ship, leading to its destruction and the abandonment of that technology. (NF - Turnaround comic: "Part IV")
In 2379, a Borg supercube invaded Federation space, led by former Admiral Kathryn Janeway as a new Borg Queen. The ship surpassed other Borg cubes technologically, being capable of literally absorbing matter. Faced with the destruction of the Federation, Captain Jean-Luc Picard activated the doomsday machine and unleashed it on the supercube. The assault almost worked, except that the cube used shunt drive to shunt behind the doomsday machine, before absorbing it. (TNG novel: Before Dishonor)