Definition - What does Marching Ants mean?
Marching ants is a slang term for an animation effect first used in the MacPaint program designed by Bill Atkinson in 1984. By today's standards, it is a rather simple animation program that simulates motion on a screen. It is most commonly seen as a moving border of dots around a selected item.
Techopedia explains Marching Ants
The marching ants effect happens when programmers create visual lines that can move from one area to the other. The common example of marching ants is the selection box in various paint and graphic design utilities, where the borderline of the box is set up to consist of moving dots or lines. Marching ants can be implemented in many ways, for example, with a frame-by-frame GIF, or a source code command to incrementally shift a series of colored pixels. It is commonly used in image and visual design tools.