A smear frame is an animation technique (similar to [[motion blur]] and [[afterimage]]s) used to illustrate high speed, where the object is depicted moving fast enough to leave a "smear" in its wake.

[[Motion blur]]: post #5605845
[[Afterimage]]: post #4991877
[[Smear frame]]: post #4389652

h6. External links
https://idearocketanimation.com/8857-animation-techniques-smear