Noun
bimedian (plural bimedians)
(mathematics) A line that joins the midpoints of opposite sides of a quadrilateral or tetrahedron
A line segment joining a vertex of a tetrahedron with the centroid of the opposite face is called a median and a line segment joining the midpoints of two opposite edges is called a bimedian of the tetrahedron. Source: Internet
Thus any plane containing a bimedian (connector of opposite edges' midpoints) of a tetrahedron bisects the volume of the tetrahedron Weisstein, Eric W. "Tetrahedron." Source: Internet