\Brach`y*di*ag"o*nal\, a. [Gr. brachy`s short +
E. diagonal.]
Pertaining to the shorter diagonal, as of a rhombic prism.
{Brachydiagonal axis}, the shorter lateral axis of an
   orthorhombic crystal.

\Brach`y*di*ag"o*nal\, n.
The shorter of the diagonals in a rhombic prism.