blue line
General term for a blue-colored line, used in maps, diagrams, or as a visual marker.
The blue line on the map represents a river.
blue-line area; illegal prostitution zone
Historical term for areas marked with a blue line on police maps where illegal prostitution occurred, roughly 1940s to 1956. Abbreviation of 青線地帯.
See also: 青線地帯
non-legal public waterway; blue-line waterway
A waterway shown by a blue line on cadastral maps that is not legally recognized as a public waterway; sometimes the waterway no longer physically exists.
In postwar Tokyo, there were several areas called blue-line districts.
On the cadastral map of this land, there is a waterway shown by a blue line.
blue-line area; illegal prostitution zone
blue-line district; area of illegal prostitution
Compound of 青 (blue) and 線 (line). The historical sense derives from the blue lines used on police maps to mark areas of illegal prostitution.