outermost layer
The exterior covering
The outermost layer is the surface or covering furthest from the center of something.
Skin is the outermost layer of the body; the crust is the outermost layer of the Earth.
The phrase appears in scientific and technical contexts describing anything with a layered structure: The outermost layer of the atmosphere gradually thins into space.
- skinBody's outer layer
- dead skinDiscarded epidermal cells
- onion skinThin translucent stationery
- surfaceOutermost boundary layer
- crustHard outer layer
pie crust · shell · egg shell · bark · tree bark · epidermis · coating · top coat · rind · peel · membrane · veneer · facade · exterior · husk · sheath · envelope · film