A soliton wave is a self-sustaining wave of energy studied as a way to propel starships at warp speed without onboard warp drive, tested by the Enterprise-D with alarming results.
Dr. Ja'Dar of Bilana III developed a method of riding a soliton wave so that ships could reach warp speeds without carrying their own engines. The Enterprise-D took part in a test in which an unmanned vessel was pushed by the wave toward a set of dissipation devices on the planet Lemma II.
The wave grew in strength and became uncontrollable, threatening to destroy the colony on Lemma II. The Enterprise had to fire torpedoes to break it up before it reached the planet.