Diagonal
/daɪˈæɡnəl/
noun
A line joining non-adjacent vertices of a polygon.
Anything forming or resembling such a line, particularly:
adjective
Joining two nonadjacent vertices (of a polygon or polyhedron).
Having slanted or oblique lines or markings.
Having a slanted or oblique direction.
Synonyms: aslant, aslope, slanted, slanting, sloped, sloping