While a square is “technically” a rectangle, a shawl is a rectangular scarf with a length longer than its width. This is by geometric definition an oblong, which is why you can sometimes find them described as such. I have also seen them described as wrap when “hijab” is being used to describe a square scarf. You may sometimes encounter the word sash; even though it usually refers to a cloth belt, it sometimes refers to any rectangular fabric. Stole is also another word used to describe rectangular scarves; traditionally, this refers to a shawl worn over the shoulders.