We're not sure what is meant by that phrase. Could you give us the quote showing how it was used?
It's reminds us of a few possible meanings.
1. It seems likely that the deepest picture of physics will have more than the three spatial dimensions we are familiar with. In some pictures there may be parallel 3-D spaces, separated from ours in one of the other dimensions.
2. Sometimes when people talk about "parallel universes" they're referring to the possibility that quantum processes may result in many different outcomes, not just one, and that these outcomes each would go its own way, without influences from the others.
3. Maybe the phrase could refer to the different pockets of ordinary space time that would emerge in some pictures of the birth of our universe.
Perhaps when you follow up we can figure out which was meant.
(published on 10/03/2011)