Definition of pixelization:
(n) :
(computing) The result of enlarging a digital image further than the resolution of the monitor device, usually 72 dpi (dots per inch), causing the individual pixels making up the image to become more prominent, thus causing a grainy appearance in the image.
(n) :
(computing) The blurring of part of an image by setting groups of pixels that are close to each other to the same color.