Source : Webster's Revised Unabridged Dictionary (1913)

Diagonal \Di*ag"o*nal\, a. [L. diagonalis, fr. Gr. ? from to
   angle; dia` through + ? an angle; perh. akin to E. knee: cf.
   F. diagonal.] (Geom.)
   Joining two not adjacent angles of a quadrilateral or
   multilateral figure; running across from corner to corner;
   crossing at an angle with one of the sides.

   {Diagonal bond} (Masonry), herringbone work. See
      {Herringbone}, a.

   {Diagonal built} (Shipbuilding), built by forming the outer
      skin of two layers of planking, making angles of about
      45[deg] with the keel, in opposite directions.

   {Diagonal cleavage}. See under {Cleavage}.

   {Diagonal molding} (Arch.), a chevron or zigzag molding.

   {Diagonal rib}. (Arch.) See {Cross-springer}.

   {Diagonal scale}, a scale which consists of a set of parallel
      lines, with other lines crossing them obliquely, so that
      their intersections furnish smaller subdivisions of the
      unit of measure than could be conveniently marked on a
      plain scale.

   {Diagonal stratification}. (Geol.) Same as {Cross bedding},
      under {Cross}, a.