Implied Motion
The suggestion of movement within a still image, created by blur, gesture, position or direction.
In depth
A photograph freezes time, so movement must be inferred. Motion blur is the most literal cue, but an unstable pose, a figure caught mid-stride with both feet off the ground, or a subject placed hard against the frame edge in the direction of travel all imply it more subtly and often more effectively.
Examples in practice
A dancer caught at the peak of a leap, entirely sharp, reads as moving because the pose cannot be held.