IPA: /ˈpɒstjʊleɪtə/
KK: /ˈpɑːstʃəˌleɪtə/
A person who makes a formal request or proposal, especially in the context of the Roman Catholic Church where they advocate for the canonization or beatification of a saint.
The postulator presented the case for the saint's canonization to the church officials.
Postulator → It is formed from "postulare" (meaning to demand or claim) and the suffix "-or" (meaning one who). The word "postulator" refers to one who makes a demand or claim, often in a formal context.
Think of someone who is 'demanding' ('postulare') something — that's why a postulator is someone who makes a formal claim.