Definition - What does Macroblock mean?
A macroblock is a processing unit in visuals and video compression, and is based on linear block revamping. This is then subdivided into transform blocks and it is further subdivided into prediction blocks. A macroblock is usually a block of adjacent pixels, typically 16×16.
Techopedia explains Macroblock
Standalone frames in a picture are called I-frames. These are divided into 8×8 blocks that are not overlapping by nature. These are called pixels. These pixels are then further rearranged into 16×16 blocks called macroblocks. Any macroblock consists of a 16×16 array of luma. These elements consist of 16×16 luma samples, and 8×8 chroma samples. Luma samples denote the brightness or the achromatic portions, while the chroma samples denote the chromatic or the colored portions. Thus, macroblocks can be thought of as 16×16 pixel areas. The JPEG image format is based on macroblocks.