Spatial vortex

From Memory Alpha, the free Star Trek reference.

A spatial vortex is a wormhole-like phenomenon that allows rapid travel over great distances.

In the Delta Quadrant, there was a spatial vortex connecting one side of the region known as the Void to the other. In the 2370s, the Malon Controller Emck used the vortex to dump antimatter waste in the Void, far from the Malon home territories. The theta radiation from the waste caused severe radiation poisoning in the Void's native inhabitants.

In 2375, Captain Kathryn Janeway of the USS Voyager was determined to destroy the vortex to stop the Malon's pollution of the Void. With support from the Void aliens, Voyager destroyed Emck's freighter and fired photon torpedoes as it entered the vortex. As the vortex collapsed, Voyager jumped into high warp and rode the shock wave to the other side. (VOY: "Night")