That game is Star Fleet Battles. SFB sizes:Historically the term dreadnaught described a new class of battleship. The next generation of battleships were always referred to as battleships.
It is a sci-fi trope that dreadnaught class battleships are your top of the line, latest super weapon.
There is a game - possibly one of the Traveller boardgames - where the dreadnaught is the class below battleship.
In S:9 all of the so called dreadnaughts (Tigress etc) have the code BB.
BB, DNH, DN, DNL/BCH, BC/CA, CM, CL/DH, DD/FB/FFB, FF, Pol, Gunboat, Heavy Fighter, Fighter.
Note that SFB CVA's are DN's, CVB's are CAs, and CVLs are CL's and DD's.
Dreadnought itself remained a term for old Battleships up to about the end of WW1, but the "current" were always Battleships. Superdreadnought was the term for these WW I era "bigger than HMS Dreadnought Battleships."
Note that Steve Cole's other game, Starfire, uses: MN (Monitor), SD (Superdreadnought), BB, BC, CA, CL, DD, FF, CT (corvette), ES.
HMS Dreadnought and the "Class of 1905" and other pre- WWI large battleships were "Dreadnoughts" or "Dreadnought Type Battleships". The even larger WWI era were Super-Dreadnought Battleships. Then, we get the WWII era Battleships that make them all look small; I've handled USN documents referring to the "Dreadnought sized battleships in NSPH" (Naval Station Pearl Harbor.)
The term has different placement within the Battleship label depending upon when one is looking at. 1905-WW1, it's the big ones. Interwar, it's the medium. WWII and Korean War era, it's the small ones; anything new & smaller is a BC, and the Old and Smaller than HMS Dreadnought was no longer in service.