Working Definition for "The Universe"

The universe is that which contains and subsumes1 all of the laws of nature and everything subject to those laws. (John Hawley and Katharine Holcomb, "Foundations of Modern Cosmology")

1 subsume: to classify within a larger category or under a general principle

The universe contains all that is physical, including SPACE and TIME.

Neither space nor time is an absolute quantity. Two observers with identical clocks and identical rulers will measure different lengths for a particular object and different amounts of time that pass between two events if:
Atomic clocks are so accurate that these effects can be measured on a single transatlantic flight! (JFK to Heathrow)

On to Meaningless Questions or back to start.