We immediately began to investigate the issue and found that there was a cascading bug in one of our infrastructure components. [..] A “cascading bug” is a bug with an effect that isn’t confined to a particular software element, but rather its effect “cascades” into other elements as well. One of the characteristics of such a bug is that it can have a significant impact on all users, worldwide, which was the case today,
Twitter Blog: Today’s turbulence explained
This is some usage of the word “explained” that I am not familiar with.