A dwarf star was any star of average or low luminosity, mass, and size.
In 2376, the USS Voyager encountered a planet that produced gravimetric readings similar to that of a collapsed dwarf star. (VOY: "Blink of an Eye")
Among the obstacles found in the 2.3 billion kilometer Antarian Trans-stellar Rally, first held in 2377, included navigating dwarf star clusters. (VOY: "Drive")