What is "jaggies"

n. (context computer graphics informal English) jagged artifacts in raster graphics, such as those caused by resize a bitmap image without preserving its aspect ratio.

"Jaggies" is the informal name for artifacts in raster images, most frequently from aliasing, which in turn is often caused by non-linear mixing effects producing high-frequency components or missing or poor anti-aliasing filtering prior to sampling.

Jaggies are stairlike lines that appear where there should be smooth straight lines or curves. For example, when a nominally straight, un-aliased line steps across one pixel, a dogleg occurs halfway through the line, where it crosses the threshold from one pixel to the other.

Jaggies should not be confused with most compression artifacts, which are a different phenomenon.