diagonally

dʌɪˈaɡ(ə)nəli
dʌɪˈaɡən(ə)li

adverb

in a diagonal direction.

now walk diagonally across the field towards a farmhouse

obliquely,at an angle,crossways,crosswise,on the cross,on the slant,slantwise,aslant,cornerwise,on the bias,cater-cornered,cater-corner,catty-cornered,kitty-corner