sandbar in an inlet; sandbank
Archaic term for a sandbar or sandbank, especially one formed in a bay or inlet. Not used in modern Japanese; replaced by 砂州 (さす) or 砂嘴 (さし).
In old documents, there are descriptions of sandbars that formed in inlets.
The exact derivation is uncertain; the kanji 浦 (inlet) and 州 (sandbank) suggest a compound describing a sandbank in a bay or inlet.