Across the short way — along the width of something, from one long side to the other, rather than down its length. Think of a piece of paper on your desk: cutting it widthways gives you two short, wide pieces; cutting it lengthways gives you two long, thin ones. You will hear it most in cooking, sewing, and craft instructions ('slice the carrot widthways', 'fold the fabric widthways'), because those are the places where the direction of a cut really matters. It is an adverb — it tells you how you cut or fold or lay something — so it comes after the verb, not before a noun. 'Widthwise' means exactly the same thing and is more common in American English; British writers use both. Its opposite is 'lengthways' / 'lengthwise'. One honest warning: even native speakers sometimes have to stop and think which is which, and a careful recipe writer will often say 'across, into rounds' instead, just to be safe.