There are three (4) kinds of spacetime:
- Spacetime is time that takes space. It takes lot of space, so mega-clocks could be spacetime.
- Spacetime is also specially designated space that takes lot of time to get in order. Your room is such example of spacetime.
It may contain stars and gravity and some Star Trek temporal phenomena. Many battles there. Combining space with time may result in spacetime, but only with appropriate cheese. Otherwise, only spacetime appears.
General spacetime equation is: