(1) See
alias.
(2) In computer graphics, aliasing is the stair-stepped appearance of diagonal lines when there are not enough pixels in the image or on screen to represent them realistically. Also called "stair-stepping" and "jaggies." See
anti-aliasing.
Low and High Resolutions
A low-resolution image showing the stair-stepping is on the left. The higher-resolution version is on the right.