Gravity well
From Memory Alpha, the free Star Trek reference
A gravity well is a distortion of the space-time continuum caused by an object with mass, which can be conceptualized on a two-dimensional surface as a depression: the "well". The curvature of the well corresponds to gravity.
The Bajoran wormhole has its own gravity well. After a carrier wave emitted from the newly established wormhole relay station created a subspace inversion in the wormhole in 2371, its gravity well increased by a factor of three. (DS9: "Destiny")
The Dyson Sphere had an immense gravity well, not least due to the star at its center but the mass of the structure itself. As no radiant sunlight light or solar wind escaped from the sphere, starships were not able to detect the sphere until they were almost on top of it. As a result the sphere's gravity well came as quite a shock to both the USS Jenolan in 2294 and USS Enterprise-D in 2369, so much so that the former was pulled in and crashed on the surface. (TNG: "Relics")
In 2369 two Quantum singularity lifeforms came into this space-time continuum to save their young who were trapped in an artificial gravity well, the engine core of the Romulan warbird. The aliens need a natural gravity well to incubate their young and thought the engine core was a natural one. (TNG: "Timescape")
It was also possible that while a planet may be found inside a rift that has the properties of a gravity well, the gravity on the planet's surface may be similar to Earth's. Tom Paris and Tuvok were stranded on such a planet while USS Voyager was nearly pulled inside a rift containing the planet. (VOY: "Gravity")
