"Dimensional gradient" was a term used as part of an advanced form of geometry used by a race of aliens who resided inside chaotic space.
In 2375, when the USS Voyager became trapped in a region of chaotic space in the Delta Quadrant, these aliens managed to make contact with Commander Chakotay, Voyager's first officer, by reactivating a gene causing him to experience a series of hallucinations, in an attempt to communicate to Chakotay a means by which Voyager could safely return to normal space. Although neither Chakotay nor the rest of the crew completely understood the mathematics involved, the aliens managed to transmit that chaotic space intersected the normal spacetime continuum at the "eighteenth dimensional gradient," and that a "paralateral rentrillic trajectory" would allow Voyager to escape. Performing the modifications, Chakotay successfully guided Voyager to safety. (VOY: "The Fight")