A belief commonly accepted, but not enjoined as a dogma or matter of faith; (hence) a belief which is not insisted on or carried out in practice (now archaic).
Origin
Mid 17th century; earliest use found in John Bramhall (d. 1663), Church of Ireland archbishop of Armagh.
Definition of pious opinion in US English:
pious opinion
noun
A belief commonly accepted, but not enjoined as a dogma or matter of faith; (hence) a belief which is not insisted on or carried out in practice (now archaic).
Origin
Mid 17th century; earliest use found in John Bramhall (d. 1663), Church of Ireland archbishop of Armagh.