used to describe a waste storage or disposal site several tens of meters underground and protected by its natural surroundings (e.g. on a hillside). Distinguished from near-surface sites (e.g. protected by an above-grade tumulus) and deep disposal sites (usually 500 m deep) in which the geological environment acts as an effective barrier

The geologic zone below the surface of the earth. Rock and soil materials lying near, but not exposed at, the Earth's surface.

Below ground surface.

Subsurface is the seventh studio album by British progressive metal band Threshold. The album was released in August 2004, and received an Album of the Month award in several European music magazines.

beneath the surface; "subsurface materials of the moon"