DIAGONAL, adjective [Gr. A corner.] 1. In geometry, extending from one angle to another of a quadrilateral figure, and dividing it into two equal parts. 2. Being in an angular direction. DIAGONAL, noun A right line drawn from angle to angle of a quadrilateral figure, as a square or parallelogram, and dividing it into two equal parts. It is sometimes called the diameter, and sometimes the diametral.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI