A warp eddy was a residual phenomenon in space that was created by the effects of warp drive. DaiMon Greko's Ferengi ship once hit a warp eddy and suffered damage to its hull. (DS9 reference: Legends of the Ferengi) When Deep Space 9 lost contact with the USS Yangtzee Kiang in the Gamma Quadrant in 2369, another runabout searching for Benjamin Sisko and the others detected the warp eddy current from the ship, allowing the Deep Space 9 crew to determine the course of the Yangtzee Kiang. (DS9 episode: "Battle Lines")