Being in the middle; running through the middle, dividing an animal into right and left halves, relating to or constituting the middle value of an ordered set of values (or the average of the middle two in a set with an even number of values), noun_ The line that joins the midpoints of the nonparallel sides of a trapezoid, The dividing area, either paved or landscaped, between opposing lanes of traffic on some highways, A line that joins a vertex of a triangle to the midpoint of the opposite side