I've recently heard the follwing sentence in a text for children learning English:
The blackboard is square.
It got translated to the German equivalent of “the blackboard is quadrilateral”. The English version felt plain wrong to me, since to me a square has to have four right angles and four edges of equal length, while blackboards tend to be wider than they are high. But since my professional interest lies with geometry, I might be overly picky when it comes to using correct terms for geometric objects.
I've seen an online dictionary use the term “square” as a possible translation for the German term for quadrilateral. The Merriam-Webster online dictionary, on the other hand, only gives the precise mathematical meaning, with no leeway for rectangles or other quads.
So I wonder, what's the common man-on-the-street interpretation of the word “square”? If presented with a definitely non-sequare rectangle (in the mathematical sense), would people call this a square by themselves, or accept square as a correct term if used by someone else? How about a quadrilateral which is not even rectangular?
The accepted answer at In daily conversation, can I call an object (eg a button) square to emphasize it's not round even though it's rectangular? suggests reserving the word “square” for things which are actually square in the mathematical sense. While I agree with that preference in active use, I'd like to gain some intuition whether diverging from this is plain wrong, or just imprecise everyday language.