|Under the level of the ground.|
Belowground storage areas.
|An electric railway operating below the surface of the ground (usually in a city).|
In Paris the subway system is called the `metro' and in London it is called the `tube' or the `underground'.
|زمین دوز برقی ریل|
زیر زمین برقی ریل
|Conducted with or marked by hidden aims or methods.|
Clandestine intelligence operations.
Cloak-and-dagger activities behind enemy lines.
A secret agent.
Secret sales of arms.
Surreptitious mobilization of troops.
An undercover investigation.