/ əˈpɒsl; NAmE əˈpɑːsl/ noun
1.
Apostle any one of the twelve men that Christ chose to tell people about him and his teachings
2.
apostle (of sth) ( formal ) a person who strongly believes in a policy or an idea and tries to make other people believe in it :
an apostle of free enterprise
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WORD ORIGIN
Old English apostol , via ecclesiastical Latin from Greek apostolos messenger, from apostellein send forth.