noun which may take the genitive case particle 'no', noun
special; exceptional; in a class of its own
Used to describe something that stands out from the rest, often in a positive sense, as being on a different level. Commonly used in the pattern 別格の + noun or 別格だ.
His talent is in a class of its own.
This hotel's service is exceptional.
別格 means treated as a special, separate case, the opposite of 同列, where things are grouped at the same level.
Compound of 別 (separate, different) and 格 (status, rank). Literally 'separate rank', referring to something that belongs to a different class.