Class V is a starship classification term used to describe a type of starship in relation to other starship types in similar fleets.
In the 24th century, the Sagan-class starship was considered to be a class V science research vessel by the Federation Starfleet. (FASA RPG module: Star Trek: The Next Generation Officer's Manual)
The SS Ranek was a Benzite Class V commercial transport ship in service in the early 25th century. (STO - Klingon War mission: "Cernan System Patrol")