under ground—below the surface of the ground:
- Attending college while working under ground is not a dream come true, but conductors are well paid.
underground—(attrib.)
1. situated or taking place below the surface of the ground:
- This difference could have been the result of the unaccounted for flow of underground waters into the lake.
2. (of a political movement, etc.) concealed and acting in secret:
- Until recently people suspected of underground activity had been arrested and court-martialed.
3. separate from a prevailing social or artistic environment:
- Although this form of underground art rarely makes it into the museums, it has attracted huge interest in recent years.