Subspace vacuole

From Memory Alpha, the free Star Trek reference

A subspace vacuole or spectral rupture is a subspace anomaly, identified by Tom Paris as a type of dimensional distortion. Subspace vacuoles occur on the Vhnori homeworld, and they use them to transport their dying, using a device known as a cenotaph; they believe that this sends the person into an afterworld known as the Next Emanation.

Harry Kim of the USS Voyager was accidentally drawn through a subspace vacuole to the Vhnori homeworld in 2371. (VOY: "Emanations")

In 2371, Voyager encountered a region densely packed with subspace vacuoles. The most expedient way to pass through was to make brief warp jumps, allowing the computer to make automatic course corrections in between. During the journey, Voyager was attacked by the Vidiians, acting on information from a future version of Kes. (VOY: "Fury")

In 2375, Harry Kim and Derran Tal explored a class 3 nebula, where they found that a subspace vacuole near the center was acting as a gravitational anchor for the surrounding gas. (VOY: "The Disease")