What makes a ship a capital ship?

What makes a warship a capital ship now that line-of-battle warfare has gone?

It is a strategically important asset whose deployment requires political-level coordination, relative to the navy that owns it.

A capital ship is a naval asset whose deployment carries consequences large enough to require high political authority. The category is therefore relative to the navy and state that own the vessel. A Norwegian frigate can be a nationally strategic asset even when a routine British frigate deployment is handled below ministerial level. The same test can include aircraft carriers and ballistic-missile submarines because their movements cannot be treated as ordinary fleet administration. Moskva's firepower and reported nuclear role placed the cruiser at least in the second rank of capital ships for Russia.