A distortion ring.
Graphic of Voyager affected by the distortion ring.
A distortion ring (also called an spatial distortion wave, or an implosion ring if it has a spatial implosion component) is a spatial anomaly where the shape of space-time itself is changing.
In 2371, the USS Voyager was caught by a moving distortion ring, which collapsed its warp field and enveloped the ship. Most of the crew were trapped in various sections of the ship, unable to reach most systems as the spatial distortions continuously reconfigured the vessel's interior. Based on tricorder data, it seemed that the ship was also slowly being crushed by a spatial implosion. Captain Kathryn Janeway was incapacitated after she contacted one of the spatial distortions.
Lieutenant B'Elanna Torres and Ensign Harry Kim managed to reach main engineering and initiate a shock pulse, but rather than dissipating the ring it accelerated the implosion. As the remaining crew members gathered in holodeck 2, at the center of the ship, the distortion ring passed through them harmlessly and disappeared. Janeway regained consciousness shortly after, realizing that the ring was a lifeform that had been attempting to communicate with her. It was found that Voyager's entire database had been copied, while 20 million gigaquads of new information had been downloaded. (VOY: "Twisted")