Universe in reality: The totality of all there is in reality.
Normally, one does not explicitly consider the universe, but only such parts or aspects of it as one is interested in. Even so, normally these parts or aspects are - if tacitly - supposed to be part of some totality of all there is.
The idea of the universe, like many supposedly all-comprising terms, tends to come with problems of a logical kind, such as: What is outside it? What went on before it came to be? Where is God in it if He exists, or is He outside of it? Are there any possible alternatives to it - alternate universes, or alternate histories of the universe - and if so, how do these relate to the universe there is?
On the given definition, the first three questions are easily answered in principle: Nothing is outside it; nothing went on before it came to be; and if there is a God, he is inside it. The last question is less easily answerable, and involves the reality of possibilities.