What is retrolisthesis of c3 mean?

Displacement: Retrolisthesis is the posterior displacement of one vertebral segment in relationship to another vertebral segment. C3 is the third cervical spinal segment. C3 may be posteriorly displaced in comparison to C2 or c4.

Malalignment: Basically, C3 is sitting posterior or slid backwards on c4. This may be a fixed listhesis which is stable, or it may be dynamic or translational and unstable.

It simply means that: The bones or vertebra of the neck which should be perfectly stacked one on top of another are not at the third vertebral level with C3 offset backwards most likely to degenerative changes.