(covers information from several alternate timelines)
In 2370, the Maquis captured a defective Cardassian ATR-4107 missile. B'Elanna Torres spent nearly a month reprogramming its computer and upgrading its systems, and eventually named it Dreadnought owing to its formidable nature. (VOY: "Dreadnought")
There are only three known on-screen references to a dreadnought; one comes from the radio chatter in the first Epsilon IX scene in Star Trek: The Motion Picture. The dreadnought named Entente, was derived from Franz Joseph's Star Fleet Technical Manual, which also states that it is a Federation-class dreadnought. The outline of a three nacelled Federation-class ship is briefly glimpsed in Star Trek III: The Search for Spock computer screens on the USS Enterprise. Another is Dreadnought, the name B'Elanna Torres chose for the captured ATR-4107 missile in VOY: "Dreadnought". The third comes from Star Trek Into Darkness, where the USS Vengeance was identified as a Dreadnought-class warship.
Dreadnought-class is briefly mentioned by William T. Riker in the novel Dark Mirror as a starship class that is the closest analog Starfleet has to the heavily-armed and armored version of the Galaxy-class from the mirror universe.
The game Star Trek Online uses the term "Dreadnought" as a distinct type of ship, usually combining the durability and movement characteristics of Cruisers with the tactical focus of Escorts. Starfleet's Dreadnought Cruiser is represented by the Galaxy X-class (β) from the TNG episode "All Good Things...". Other playable ships belonging to different factions in the game are also classified as "Dreadnought", including the Scimitar Warbird, the Jem'Hadar battleship (though the game calls it a "dreadnought carrier"), the Xindi-Aquatic cruiser (also reclassified as a dreadnought carrier) and other game-exclusive designs. Dreadnought ships are also equipped with combat-capable hangar bays and can launch fighter ships in battle.