On the one hand, I read on Wikipedia that
[A] matrix (plural matrices) is a rectangular array of numbers, symbols, or expressions, arranged in rows and columns.
However, googling "3D matrix" produces a huge number of hits, including many from this website.
I also find some people complaining about alleged misuse of terminology, e.g. here
Just to gratify a pet peeve, there is no such thing as a "3D matrix". Matrices are 2D by definition.
What's the most appropriate terminology here, say for a high school or undergraduate mathematics teaching context?