ukośne in English:

a tie with diagonal stripes

The Scottish flag is the St Andrew’s cross — two white, diagonal bands — on a blue background.

When vertical and horizontal forces are applied, the resultant acts in diagonal direction.

diagonal /daɪˈæɡənl; US / adj. 1 (used about a straight line) joining two sides of sth at an angle that is not 90° or vertical or horizontal Draw a diagonal line from one corner of the square to the opposite corner. ▶ przekątny

Slice the vegetables on the diagonal.

A diagonal matrix is positive semidefinite if and only if all of its elements are nonnegative.