Imaginary line running along the top of non-ascending, lowercase letters.
The meanline falls at the top of many lowercase letters such as “e,” “g” and “y.” It is also at the curve of letters like “h.”
In typography, the mean line, also (and more simply) known as midline, is the line that determines where non-ascending lowercase letters terminate in a typeface. The distance between the baseline and the mean line is called the x-height.
Round glyphs will break (overshoot) the mean line slightly in many typefaces, since this is aesthetically more pleasing; a rounded shape will appear visually smaller than flat topped (or bottomed) shapes of equal height, due to an optical illusion.