What does the vision term axis mean?

"Axis" is a term most often used in describing the orientation of Astigmatism. If you look at your written eyeglass prescription, it may say something like "-2.00-1.00X180". What this means is that you have two diopters of myopia (nearsightedness) and one diopter of astigmasim at axis 180. Axis 180 tells you that the orientation of the astigmatism correction is horizontal. Axis 90 would be Vertical. Axis 045 or 135 would be oblique. And it could be any axis from 1 to 180 degress. The degree of the axis depends on the type of astigmatism you have.