The Collaborative International Dictionary of English v.0.48:
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
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
Diagonal stratification. (Geol.) Same as Cross bedding,
under Cross, a.