Blockout - Opaque - Light-impermeable
The terms blockout, opaque and light-impermeable are often used synonymously. They all mean the same thing: no light gets through. Blockout is usually the addition for the banner material. Blockout material usually has a separate barrier layer that is light-impermeable.
The word “opaque” derives from the Latin opacus (“dark”, “shaded”) and entered today's usage via the French opaque.
Some banner materials have a visible blockout layer and are black or grey on the back. Others have this layer in the middle and may also be printable on the back.