a. [ Gr. me`sos middle. ] (Anat.) Middle; median; in, or in the region of, the mesial plane; internal; -- opposed to lateral. [ 1913 Webster ]
Mesial plane. (Anat.) See Meson. [ 1913 Webster ]
adv. (Anat.) In, near, or toward, the mesial plane; mesiad. [ 1913 Webster ]