There are actually multiple definitions that have arisen as our understanding of the cosmos has grown [1]. The word has always been a filler for "all the stuff there is" but as science has evolved it's become useful to make a distinction based on "all the stuff there is in <whatever>".

The context of this article makes it pretty clear that a brane-constrained definition is being used.

[1] http://en.wikipedia.org/wiki/Multiverse#Max_Tegmark.27s_four...