A time eddy was a distortion in the space-time continuum.
Whitaker used time eddys to transport dinosaurs from the past to 1970s London as part of Operation Golden Age. A 12th century peasant was inadvertently transported too. (TV: Invasion of the Dinosaurs)
The Thirteenth Doctor once got trapped in a time eddy. She contacted human and Zygon Osgood via text message at some point in 2020, complaining about the boredom it induced for her. (WC: The Zygon Isolation)