The Collaborative International Dictionary of English v.0.48:

Median \Me"di*an\ (m[=e]"d[i^]*an), a. [L. medianus, fr. medius
   middle. See Medial.]
   1. Being in the middle; running through the middle; as, a
      median groove.
      [1913 Webster]

   2. (Zool.) Situated in the middle; lying in a plane dividing
      a bilateral animal into right and left halves; -- said of
      unpaired organs and parts; as, median coverts.
      [1913 Webster]

   Median line.
      (a) (Anat.) Any line in the mesial plane; specif., either
          of the lines in which the mesial plane meets the
          surface of the body.
      (b) (Geom.) The line drawn from an angle of a triangle to
          the middle of the opposite side; any line having the
          nature of a diameter.

   Median plane (Anat.), the mesial plane.

   Median point (Geom.), the point where the three median
      lines of a triangle mutually intersect.
      [1913 Webster]