Definition of: diagonal

(dī·ag′ə·nəl) adjective
1. Crossing obliquely; oblique.
2. Marked by oblique lines or the like.
3. Geom. a Joining two non–adjacent or reentering angles of a figure: a diagonal line. b Joining, as a plane, two non–adjacent edges of a solid.
—noun
1. Geom. A straight line or plane passing from one angle, as of a square, to any other angle not adjacent.
2. A fabric woven with diagonal ridges or lines: also diagonal cloth.
3. Anything running diagonally. [<L diagonalis <diagonios <dia- across + gonia angle]
—di·ag′o·nal·ly adverb