location without an address; unnumbered plot of land
Refers to a piece of land or a location that does not have a registered address or lot number, often in rural or undeveloped areas.
That hut is on an unaddressed plot of land, so mail doesn't reach it.
Places marked as 番外地 on the map have no assigned address.
Compound of 番外 (bangai, 'outside the numbering') + 地 (chi, 'land'). The term is used in Japanese land registration to denote parcels without an assigned lot number.