connecting two nonadjacent corners of a plane figure or any two corners of a solid that are not in the same face

an oblique line of squares of the same color on a checkerboard

(mathematics) a set of entries in a square matrix running diagonally either from the upper left to lower right entry or running from the upper right to lower left entry

(geometry) a straight line connecting any two vertices of a polygon that are not adjacent

a punctuation mark (/) used to separate related items of information

a line or cut across a fabric that is not at right angles to a side of the fabric