Dreadnoughts are massive battleships (hull size 20+). They have a large array of weapons, and might even have fighter capacity. Years after the Second Sathar War ended, they were developed to replace battleships as the flagships of the UPF Strike Force fleets, and served as the pinnacle of a planet's defense until the development of the Fortress Ship.
The only known class of dreadnought is the Battlestar-class. The Battlestar-class dreadnought is made up of an upgraded battleship, with a pair of fighter carriers mounted on struts.
(the Battlestar-class ship is based on Battlestar Galactica)