Dictionary of Computer and Internet Terms: artifact
artifact
any unwanted part of a signal or image that results from the way it was recorded or processed. For instance, a low-level hiss is a familiar artifact of tape recording.
If you greatly increase the brightness or contrast of a JPEG image, you may see unusual stripes or blocks of color. They are artifacts of JPEG compression, in parts of the picture where the JPEG algorithm chose to sacrifice low-contrast detail in order to make the file smaller.
