What is axial magnification?

Some articles on magnification, axial magnification, axial:

Perspective Distortion (photography) - Optics
... The transverse magnification is related by The axial magnification of an object at is the rate of change of the lens-image distance as the lens-object ... For an object of finite depth, one can conceive of the average axial magnification as the ratio of the depth of the image and the depth of the object One can see that if magnification remains ... away from the object to maintain the same magnification M, objects seem shallower, and the axial distances between objects seem shorter ...