A square is a special case of a rectangle. What is a single-word term for a rectangle that is not a square? I am looking for a word that excludes squares. I am also looking for a word that is not "rectangle".
My suggestion is : "A rectangular with two distinct sidelengths"
If you talk about one specific rectangular, you can just call it a rectangular. This usually implies that you do not mean a square because you did not name it a square.
But if you are talking about rectangulars in general, usually squares are included.
I do not know whether there is a common name.