So I was in C++, and we had third graders come today to play our programs. Whilst the others just drilled them with problems, my game was subtract a square. It was fun watching them discover that numbers like "9" were bad positions (I never explicitly referred to squaring, I just had them multiply the number by itself.) I decided to draw something like this on the board, to show the geometric connection:

The teacher called their attention that I had drawn "arrays" on the board, and they were still used in High School. I didn't bring it up, but I was wondering what they meant by "arrays".
- Is it an another name for square?
- Is it a multiplication method?
- Do they mean multidimensional arrays, as in programming? (If so, third grade has sure advanced since I was in school!)
- Something else?
These were USA/Pennsylvania third graders, if that helps.
Note: I know various meanings of "array", but I am wondering what they could possibly mean in this context, with a third grade teacher explaining to their students.

You are correct. The photos that you posted are examples of multidimensional arrays. It makes sense as well since the definition of an array is an arrangement of objects that can be constructed in rows and columns.