Definitions for "Chromakey"
The replacement of a colour or colour range with another image or colour. The most common use is a blue screen, which allows a different background to later be added to a scene to create a special effect.
Professional trick for seamlessly inserting part of one video picture into another - used for special effects, such as making Superman fly.
The process of isolating portions of an image according to the chroma (or colour) of the image. Chromakey is typically used with blue or greenscreen shots.