The Collaborative International Dictionary
Orbital index
Orbital \Or"bit*al\, a.
Of or pertaining to an orbit. ``Orbital revolution.''
--J. D.
Forbes.
Orbital index (Anat.), in the skull, the ratio of the vertical height to the transverse width of the orbit, which is taken as the standard, equal to 100.
Wiktionary
orbital index
n. (context anatomy English) In the skull, the ratio of the vertical height to the transverse width of the orbit, which is taken as the standard, equal to 100.