A temporal aperture in the engine core of a Romulan Warbird
A temporal aperture is a breach in the spacetime continuum which can have the effect of disrupting the flow of time.
Such a phenomenon was encountered by the crew of the USS Enterprise-D in 2369. The aperture had formed as a result of a power transfer beam interacting with a Romulan Warbird's artificial quantum singularity, which itself was being used as a nest by a race of aliens from another time continuum. This aperture had the effect of disrupting spacetime around the ships, resulting in the formation of a series of temporal fragments in which time progressed at a relatively accelerated or decelerated rate. The fragments were later eliminated when Commander Data was able to manipulate the aperture by remodulating his tricorder's delta band emissions, making time run backwards. This gave the Enterprise crew a chance to disrupt the transfer beam before it fragmented spacetime. (TNG: "Timescape")