Ian Henry of the Tabletop blog has coined this rather useful gaming term (which somehow the apparently million-word-strong* English language has not yet thought it necessary to include). I just spotted it in his recently posted discussion of the abstract Ataxx, although Google tells me that he first used it last month.
In case his meaning is not immediately clear (although it really ought to be) he’s created what grammarians would refer to as a ‘portmanteau’ word: a combination of ‘diagonally’ and ‘orthogonally’. So, for example, a chess piece placed on a square somewhere in the middle of a chessboard could be said to have eight ‘diathogonally’ adjacent spaces. Handy!
Given how often this concept is used in all sorts of contexts the word really deserves more widespread adoption. And if you do indeed spot it cropping up elsewhere, well, you heard it here
* Nonsense, obviously. More reliable sources suggest the total is more like 250,000 (still quite a lot, it must be said) of which roughly 1 in 5 aren’t even used anymore.