Definition of diagonals:
(adj) :
(geometry) Joining two nonadjacent vertices (of a polygon or polyhedron).
(n) :
(geometry) A line joining non-adjacent vertices of a polygon.
(adj) :
Having a slanted or oblique direction.
(adj) :
Having slanted or oblique lines or markings.
(n) :
(geometry) A line or plane at an oblique angle to another.
(adj) :
Of or related to the cater-corner (diagonally opposite) legs of a quadruped, whether the front left and back right or front right and back left.