Motion blur refers to the visual effect of capturing movement in an image or video, resulting in a blurred or smudged appearance. While commonly used in photography and film, there are several synonyms to describe this phenomenon. One such word is "velocity blur", which emphasizes the speed at which the object is moving. Another synonym is "action blur", as it emphasizes the movement and dynamic nature of the subject. "Dynamic blur" is another synonym that emphasizes the sense of motion captured in the image or video. Ultimately, the term used may depend on the context and the desired emphasis on movement and velocity in the final product.