1Mathematics a line that is the geometric mean (mean proportional) between two lines whose lengths are incommensurable, but the squares of which are commensurable (only with reference to or in translations of Euclid's work).
2Generally a line through the middle of something.
3Anatomy and Zoology= median line.
Origin
Late 16th century.
Definition of medial line in US English:
medial line
noun
1Mathematics a line that is the geometric mean (mean proportional) between two lines whose lengths are incommensurable, but the squares of which are commensurable (only with reference to or in translations of Euclid's work).
2Generally a line through the middle of something.