Subspace variance

A subspace variance was a phenomenon in subspace that is created by a cloaked ship at warp.

In 2371, Jem'Hadar vessels detected a subspace variance from the cloaked USS Defiant (NX-74205) (I). T'Rul advised Benjamin Sisko to have the Defiant drop out of warp to stop the variance. 

In 2383, Sisko ordered the USS Defiant (NX-74205) (II) to drop out of warp while cloaked to eliminate a subspace variance. Wheeler Stinson was unaware of the phenomenon.