Also called "elongated inbetween." But Smear is most used. #animation
Unlike traditional movement in animation, which uses key frames (to plot beginning/ending points) and in-between-frames (to create the illusion of movement), smearing depicts one quick “blur” of motion in a single frame. As a result, it creates the sensation of a sudden burst of speed. And also as a result, back in the early 1940’s, it was frowned upon as being a lazy way to depict movement. This did not bode well, at least not at first, for The Dover Boys animator Chuck Jones.