A plasma drift is a nebula-like interstellar phenomenon.

A large plasma drift moved through the Talaxian system when Neelix was a child, blocking out the stars and moons for months. (VOY: "The Haunting of Deck Twelve")

In 2372, the USS Voyager entered a plasma drift almost half a sector long, to hide from a Vidiian-controlled star system. Upon leaving the drift, they encountered some subspace turbulence that was in fact a divergence field. (VOY: "Deadlock")