Subspace eddy
A subspace eddy was a potentially disruptive spatial phenomenon.

In 2152, the Vulcan starship Seleya became caught in a subspace eddy while attempting to chart the thermobaric clouds at the perimeter of the Delphic Expanse. As a result, the Seleya was pulled into the Expanse, and all contact with the ship was lost. ()

In 2378, the  passed through a subspace eddy. Captain Kathryn Janeway suspected it was the wake of another ship. The Doctor dismissed it as probably just the gravimetric shear from a nearby Mutara class nebula. The eddy turned out to be the wake of a Hierarchy survey vessel. ()

See also
Astral eddy
Plasma eddy
Warp eddy

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eddy