This is the 5715th most frequent Dutch word.
nationaal
"Nationaal" means "national" in English.
In this case, 'nationaal' modifies 'kampioen', denoting their victory or title at a nationwide level.
De nationaal kampioen werd gehuldigd na de wedstrijd.
The national champion was celebrated after the match.
This usage of 'nationaal' implies a scale or level of recognition within the nation, modifying 'bekende'.
Ik geniet van nationaal bekende muziekartiesten.
I enjoy nationally known music artists.
Here, 'nationaal' functions as an attributive adjective describing the museum, indicating its significance at a nationale scale.