Meaning of “diagonal” - Learner’s Dictionary

diagonal

adjective uk us /daɪˈæɡənəl/
SLOPING

A diagonal line is straight and sloping and not horizontal or vertical:

a tie with diagonal stripes
SQUARE

going from the top corner of a square to the bottom corner on the other side

diagonally adverb

(Definition of “diagonal” from the Cambridge Learner’s Dictionary © Cambridge University Press)