Universe

From Encyclopedia Jumpleadia

A Universe is a point within the Multiverse. There are an infinite number of Universes, many of them virtually indistinguishable from others. New Universes are created whenever people, animals or objects perform any action - the alternate actions and outcomes are played out in these alternate universes.

Alternate universes are also referred to as dimensions and realities, although a reality is not necessary a Universe, nor is a dimension. It's a sort of lovely catch-all science fiction term, though, isn't it?