This is the 8893rd most frequent Russian word.
провозглашен
"Proclaimed."
The word 'провозглашён' is used in the passive form to indicate that he was officially declared or proclaimed by someone as a hero.
Он был провозглашён героем города после спасательной миссии.
He was declared a hero of the city after the rescue mission.
Here, 'провозглашён' serves to denote that the law was officially stated or recognized as fundamental.
Новый закон провозглашён основой для реформ.
The new law has been declared as the basis for reforms.
'Провозглашён' is used in this sentence to mean that the day was officially announced as a holiday.