Definitions of underground

1. The place or space beneath the surface of the ground; subterranean space.

2. A place beneath the earth's surface.

3. A place or space beneath the surface of the ground.

4. A space beneath the surface of the ground.

5. beneath the surface of the earth; " water flowing underground"

6. in or into hiding or secret operation; " the organization was driven underground"

7. Beneath the surface of the earth.

8. Beneath the surface of the ground; secretly.

9. under the level of the ground; " belowground storage areas"; " underground caverns"

10. conducted with or marked by hidden aims or methods; " clandestine intelligence operations"; " cloak- and- dagger activities behind enemy lines"; " hole- and- corner intrigue"; " secret missions"; " a secret agent"; " secret sales of arms"; " surreptitious mobilization of troops"; " an undercover investigation"; " underground resistance"

11. Being below the surface of the ground; as, an underground story or apartment.

12. Done or occurring out of sight; secret.

13. Under the earth; hidden.

14. Under the surface of the ground.

15. Situated, done, or operating beneath the surface of the ground.

16. Done in secret.