Why super-battleship labels lose their meaning

What would qualify as a super battleship, and could it be a useful category?

The term can simply mean the latest generation until rivals catch up, as with Orion's super-dreadnought label.

A ship does not need to reach an impractical size to acquire a super-battleship label. Such terms can simply identify the newest and most powerful generation until competitors catch up. The Orion class was called super-dreadnoughts and was then surpassed by the Queen Elizabeth class. The description is therefore relative to contemporary ships rather than a permanent technical category.