virgin land; uncultivated land
Refers to land that has never been cultivated or developed; often used in geographical or historical contexts.
The pioneers cultivated the virgin land.
unexplored area; frontier
Metaphorical extension: an area of study, research, or activity that has not yet been explored or developed.
This research field is still unexplored territory.
Compound of 処女 (virgin) and 地 (land). The metaphorical sense is a calque from English 'virgin territory'.