Subsurface

Origin

- + surface

Full definition of subsurface

Noun

1. Something that is below the layer that is on the surface.Before we could lay the flooring we had to lay a subsurface under it to keep it flat and supoort it.
2. (countable, mathematics) A surface which is a submanifold of another surface.

Adjective

1. below the surfacevariations in subsurface conditions----