Meaning of church flag in English:
church flag
noun
NauticalA flag flown on board a ship to indicate a religious service is taking place.
In the British Navy, the church flag is a white pennant with a St George's cross in the hoist and striped red over white over blue in the fly. In the United States Navy, it is a white pennant with a blue cross.
Origin
Mid 19th century; earliest use found in Sailor's Magazine.
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