rannajoone lähedal, rannajärsaku jalamile lainetuse kulutusel tekkinud koobast meenutav õnarus/orvand, a cave like formation at the foot of the coastal cliff formed when the destructive waves hit against the cliff face producing an overhang. This overhang grows in size as the cliff is undercut, until it collapses under its own weight coasing thus a stepwize inland retreat of a cliff.