What is sideways recursion

A friend of mine is studying business analytics, currently on the topic for Microsoft DAX, but he is very new to the technological field. He mentioned yesterday, during a conversation, the term "sideways recursion". Does anyone have idea what that means? I know a regular recursion(maybe direct recursion is the more proper term), where a function calls itself directly. I know of indirect recursion, where a function calls another and then the other calls the first one back. I also know that direct recursion has some sub-types – head / tail recursion – the tail recursion is when the inner call does not participate in any calculations including the current context (e.g. the recursive call is the last statement in the function) – this is very useful lately in functional languages to optimize recursive calls, by not keeping the current context in the stack, since it will not be needed when returning back from the recursive call. Those optimizations make functional languages as effective as imperative programming languages and allow the immutability of functional languages to become practical for traditional tasks, but also allows to implement parallelism automatically to some extent … as far as I know this is why functional programming languages started to become modern lately. I have also heard of variadic template recursive functions in C++, which allow to write recursive function with arbitrary number of arguments (not sure if arbitrary type is allowed as well). But I cannot find anything about "sideways recursion" … is there a chance Microsoft is using this term instead of one of the above mentioned? E.g. instead of "tail recursion" … or maybe instead of "variadic template recursive function" (even though this one is not exactly separate type of recursion, but more a technology paradigm from the language C++)? Any help on making my knowledge on recursion classification and technology paradigms around different types of recursion would be appreciated! Thanks in advance! 🙂