I've heard this term mentioned in conversations, but I don't see it in the Bible.
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It was a circle where people gather in as they walk in a circle or in an area while they prayed. Praying boldly and being persistent always, although the bible doesn't give a specific way of doing it. God is omnipresent and whether you're in a crowd or alone in your home or car, God will answer your prayer according to His will in glory.