Trimetric fracture
From Memory Alpha, the free Star Trek reference
A trimetric fracture is a type of energetic spatial disturbance that allows chaotic space, a parallel universe, to overlap a region of normal space. Inside the zone, the laws of physics are in a state of flux.
Trimetric fractures are several light years across, inside which chaotic space intersects the prime universe at the eighteenth dimensional gradient. The fracture randomly shifts tens of thousands of kilometers through space every few minutes. Fractures appear and disappear throughout the Milky Way Galaxy randomly and unexpectedly. Ships might remain trapped in a fracture for years. It was theorized that some of the Federation starships mysteriously lost in the Alpha Quadrant may have fallen prey to this phenomenon.
A fracture encountered in the Delta Quadrant by USS Voyager in 2375 was linked to a region of chaotic space, home to an alien species. A signal on an isolinear frequency was used by an alien reconfiguration of the genes of some humanoids who became trapped inside the fracture in order to communicate the instructions to find a way out. (VOY: "The Fight")
