The phrase "diagonal stripes" refers to a pattern of straight lines that slant from one corner to another in a sloping or angled manner. Full definition
Its design consists of a central rectangle with diagonal stripes in yellow, pink, blue, and red hues. (chairish.com)
Take a peek at the image immediately below regarding the width of the white strip relative to the red diagonal stripe located in the upper left corner. (thepurplepaintedlady.com)
I can't say no to diagonal stripes because I always feel that they make me look taller and slightly slimmer. (racheldinh.com)