undergrounding

an underground car park.

an underground nuclear test

underground resistance to the tyrant.

underground trade in weapons.

There is an underground park here.

There is an underground room in the old house.

underground caverns; underground missile sites.

Recently they have laid an underground pipeline.

the New York underground art scene.

Is Tom underground?” “No, he is at grass.”

workers undergrounding telephone lines.

It was like the Black Hole of Calcutta on the underground this morning.

The house has an underground passage.

This is the biggest underground lake yet discovered.

Geological radar is a non-destructive test instrument that detect the underground objects by the quality of discontinuousness of the underground medium.