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Any persons originating from the delta area of northern California, typically displaying distinct behaviors and mannerisms isolated to the region.
Wow, that Kelly sure is a river billy, she's delta through and through.
by J-st November 25, 2011
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2
A redneck, like a hillbilly but instead of being in the hills and mountains riverbilly leave near a river.
Josh is no hillbilly, he is a damn riverbilly

That riverbilly is out fishing again for the third time.
by Makermaker May 18, 2017
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