Marco Russo and Alberto Ferrari disambiguate a pair of operators:
Have you ever wondered what the subtle difference between ALL and ALLCROSSFILTERED might be? The family of ALL functions and modifiers includes some common functions, like ALL and ALLSELECTED, and some fancier and less frequently-used functions, like ALLNOBLANKROW and ALLCROSSFILTERED. This article discusses what ALLCROSSFILTERED is, why it is there in DAX, and when and how developers should use it.
Read on for that answer, along with several helpful demos.