underpainting

As an acronym base

is b'''uilding'', '''''a'''ntenna-tower'', '''''s'''pan'', '''''e arth .

As a noun underpainting is

(arts) an initial layer of paint, often monochromatic, applied to a ground as a base for subsequent layers.

As nouns the difference between ground and underpainting

is that ground is (senseid)(uncountable) the surface of the earth, as opposed to the sky or water or underground while underpainting is (arts) an initial layer of paint, often monochromatic, applied to a ground as a base for subsequent layers.

As a verb ground

is to connect (an electrical conductor or device) to a ground or ground can be (grind).

As an adjective ground

is crushed, or reduced to small particles.

As an adjective monochromatic

is having only one color, represented by differing hues and tints for example shades in a black and white television.

As a noun underpainting is

(arts) an initial layer of paint, often monochromatic, applied to a ground as a base for subsequent layers.

As nouns the difference between paint and underpainting

is that paint is a paint horse while underpainting is (arts) an initial layer of paint, often monochromatic, applied to a ground as a base for subsequent layers.

As nouns the difference between layer and underpainting

is that layer is a single thickness of some material covering a surface while underpainting is (arts) an initial layer of paint, often monochromatic, applied to a ground as a base for subsequent layers.

As a verb layer

is (ambitransitive) to cut or divide (something) into layers.