Ah that is interesting. In my head Monitors are always slow, lumbering, decently armed and heavily armored ships.
Just have no clue how to name these otherwise.
They are not frigates, destroyers, cruisers or battleships, because those are quite universal ships, capable of decent independent routes, not local defence only.
They are not corvettes or cutters, because of their decent size and stationary endurance.
They are not bases or forts, because of their high velocity.
They are not branders, because of their conventional weapon systems.
The only alternative I was capable to think out is "Heavy Interceptor", but it's quite clumsy, I think.
So in my star nations Defence Monitors are these - in accordance with etymology, and not with "wet navies" historical patterns.