believer has definitions from the field of religion
1
[ noun ] a supporter who accepts something as true

Synonyms

truster

Used in print

(Booton Herndon, "From Custer to Korea, The 7th Cavalry"...)

Brevet_Major_General_George_Armstrong_Custer was the regiment 's first permanent commander and , like such generals as George_S._Patton and Terry_de_la_Mesa_Allen in their rise to military prominence , Custer was a believer in blood_and_guts warfare .

2
[ noun ] (religion) a person who has religious faith

Used in print

(Gibson Winter, The Suburban Captivity of the...)

If it were primarily a believing fellowship , it would recruit believers from all social and economic ranks , something which most congregations of the New Protestantism ( with a_few notable exceptions ) have not been able to do .

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