1. Relating to, located in, or extending toward the middle. 2. Of, relating to, or situated in or near the plane that divides a bilaterally symmetrical animal into right and left halves; mesial. 3. Relating to or constituting the middle value in a distribution. 4. A median point, plane, line, or part. 5. The middle value in a distribution, above and below which lie an equal number of values. 6. A line that joins a vertex of a triangle to the midpoint of the opposite side. 7. The line that joins the midpoints of the nonparallel sides of a trapezoid.
